Derivatives Of Polyunsaturated Fatty Acids Research Articles

Modulation of lipid derived mediators by polyunsaturated fatty acids

Cell stimulation by a number of agonists triggers the formation of products of lipid hydrolysis, which act either as intracellular mediators of signal transduction or as modulators of cell-cell interactions. This process is mediated by the activation of hydrolytic enzymes, the phospholipases (PLase), especially the A 2 and C, acting on cell phospholipids (PL). Among the major products being formed, the following: a) the inositol phosphates (IP), especially IP 3, and diacylglycerols (DAG) generated intracellularly from phosphoinositides through PLase C, b) the eicosanoids, the arachidonic acid (AA) metabolites produced through combined PLase A 2 and (cyclo- and lip-) oxygenase activities, and released from cells, c) the ether lipid PAF, derived from alkylacyl phosphatidylcholine through PLase A 2, have attracted the attention of investigators for their important biological roles. Interest has also been recently developed towards products of sphingolipid hydrolysis, sphingosine and ceramide, which are generated by various cell types after stimulation, and exert biological activities. Cell glycerophospholipids are rich in long-chain polyunsaturated fatty acids (PUFA) of the n-6, namely AA 20:4 n-6, and n-3, mainly docosahexaenoic acid (DHA) 22:6, series. These compounds are differentially distributed among the various PL classes and their levels in cells are modulated through the intake with the diet of either the 18-C fatty acids (FA), precursors, linoleic 18:2 n-6, and, alpha-linolenic 18:3 n-3, respectively-followed by conversion to their long-chain PUFA derivatives, or through the intake of the preformed compounds. Levels of the long-chain PUFA in membranes can also be modulated in cultured cells, through manipulation of the supply with the growth medium. The incorporation of exogenous FA in cell lipids, in this type of study, however, follows patterns which are different from those observed in vivo after dietary manipulations. The levels of long chain n-6 and n-3 PUFA in cell phosphoglycerides modulate the generation of lipid derived mediators, in various types of cells, after in vitro stimulation. These effects can be ascribed to various mechanisms: 1. 1. Changes in eicosanoid production as a consequence of: a) changes in the levels of AA, the major precursor of these compounds, b) accumulation of long-chain PUFA of the n-3 series, which act as precursors (e.g. eicosapentaenoic acid (EPA), 20:5) of eicosanoids with biological activities different from those of the products derived from AA, or inhibitors (EPA) and/or modulators (DHA) of the AA oxygenases. 2. 2. Changes in the stimulated formation of other products of PL hydrolysis, such as the IP and PAF, possibly as a consequence of a modified micro-environment of the PLases, or as a consequence of modified eicosanoid production. The fomation of other mediators, such as the cytokines, in specialized cells, is also affected by changes of cell PUFA, possibly as an additional consequence of altered eicosanoid formation. In this presentation, examples of changes of cell n-6 and n-3 PUFA, obtained in circulating cells (e.g. platelets, leukocytes) through feeding studies in animals and humans, or induced in cultured cells after FA supplementation, will be presented and discussed, in relation to the effects on the production of eicosanoids and other lipid derived mediators.

High-performance liquid chromatography—thermospray mass spectrometry of hydroperoxy polyunsaturated fatty acid acetyl derivatives

A method for the analysis of hydroperoxy polyunsaturated fatty acids was developed. The hydroperoxy groups were acetylated by acetic anhydride, and the mixture was partially purified on a Sep-Pak C 18 cartridge and analysed by high-performance liquid chromatography with thermospray mass spectrometry. Generally, the base ion, [M + H − n(60)] + or [M + H − n(60) − n(H 2O)] +, is produced through elimination of acetic acid or water ( n = number of hydroperoxy groups). The detection limit for these derivatives was ca. 1 pmol at concentrations of hydroperoxy polyenoic acids prior to derivatization. Using this method, many hydroxy and hydroperoxy polyunsaturated fatty acid derivatives could be detected simultaneously within 30 min on a selected-ion monitoring detection chromatogram without a gradient system. The assay was successfully applied to hydroxy and hydroperoxy polyunsaturated fatty acids from an incubation mixture of rat brain homogenate to which polyunsaturated fatty acids had been added.

Lipoxins: a new series of eicosanoids (biosynthesis, stereochemistry, and biological activities).

The oxygenation of arachidonic acid and other polyunsaturated fatty acids by a wide variety of cell types results in the formation of several structurally distinct classes of biologically active compounds. These compounds include the prostaglandins, thromboxanes, leukotrienes, and other oxygenated derivatives of polyunsaturated fatty acids. A most recent addition to this family of biologically active compounds is the lipoxins (Figure 1). Leukotrienes and lipoxins are formed by mechanisms which involve initial oxygenation of free fatty acids by lipoxygenases. In general, lipoxygenase products display a wide range of actions and appear to be involved in immunity, the regulation of inflammation, and other physiological and pathophysiological processes. In this chapter we describe results of recent studies on the isolation, biosynthesis, stereochemistry and biological activities of this new series of compounds (lipoxins).

PHYSIOLOGICAL ROLES OF PROSTAGLANDINS AND OTHER EICOSANOIDS IN INVERTEBRATES.

Prostaglandins and other biologically active derivatives of polyunsaturated fatty acids have been detected in a large number of invertebrate species. A brief summary of the mammalian background of arachidonic acid metabolism is provided, and the physiological significance of these compounds in invertebrates is reviewed. Topics include regulation of ion flux, temperature regulation, reproductive biology, cell aggregation, and host-parasite interactions. Finally, perspectives on current and possible future research are offered.

Ultraviolet B Irradiation Induces Changes in the Distribution and Release of Arachidonic Acid, Dihomo-γ-linolenic Acid, and Eicosapentacnoic Acid in Human Keratinocytes in Culture

There is increasing evidence that derivatives of 20-carbon polyunsaturated fatty acids, the eicosanoids, play an important role in the inflammatory responses of the human skin. To better understand the metabolic fate of fatty acids in the skin, the effect of ultraviolet B (UVB) irradiation (280-320 nm) on the distribution and release of 14C-labeled arachidonic acid, dihomo-gamma-linolenic acid, and eicosapentaenoic acid in human keratinocytes in culture was investigated. Ultraviolet B irradiation induced the release of all three 14C-labeled fatty acids from the phospholipids, especially from phosphatidylethanolamine, and this was accompanied by increased labeling of the nonphosphorus lipids. This finding suggests that UVB induces a significant liberation of eicosanoid precursor fatty acids from cellular phospholipids, but the liberated fatty acids are largely reincorporated into the nonphosphorus lipids. In conclusion, the present study suggests that not only arachidonic acid but also dihomo-gamma-linolenic acid, and eicosapentaenoic acid might be involved in the UVB irradiation-induced inflammatory reactions of human skin.

Prostaglandins in Insect Reproduction

Prostaglandins (PG's), derivatives of certain C20 polyunsaturated fatty acids (PUFA's), feature a five-membered ring that is variously substituted at C9 and C11, and two aliphatic chains. PG's have so far been found in tissues from over a dozen insect species, most often detected by radioimmunoassay, but in some cases verified by rigorous chemical methods. Certain PG's release egg-laying behavior in two cricket species, and to a lesser extent in a moth; however, this is not true for all insects. In the field cricket Teleogryllus commodus (Walker), PG's formed in spermathecae following spermatophore transfer of a PG-synthesizing enzyme complex and precursor PUFA's release a bout of egg-laying that produces hundreds of individually deposited eggs. Insects obtain the PG precursor PUFA's either directly in their diet, or else produce them; three patterns of fatty acid metabolism are described, one of which includes de novo biosynthesis of PUFA's. Work on biochemistry of PG-synthetase activity indicates that certain, but not all, nonsteroidal anti-inflammatory drugs that inhibit PG synthesis in mammals also inhibit PG synthesis in insect systems.

Calcium translocation by fatty acid derivatives in a two-phase partition model. Structure-activity relationships

The relationship between structures of fatty acid derivatives, long-chain fatty alcohols, phospholipids and their calcium-transporting activity was investigated using the two-phase model system in which 45Ca is transported from an aqueous to an immiscible organic phase. Calcium translocation by all saturated and unsaturated fatty acids was significant only at 10 mM concentrations, but minimal or negligible below 1 mM; the corresponding methyl esters and alcohols were inactive at 10 mM. Polyunsaturated fatty acid derivatives, prepared by incubation with lipoxygenase (linoleate: oxygen oxidoreductase; EC 1.13.11.12) or by autoxidation in air, showed a markedly increased potency over the parent compounds. The oxidation products of linoleic and arachidonic acids were most potent. For example, the equieffective concentrations were 10 mM for linoleic acid, 0.4 mM for its lipoxygenase metabolites and 0.094 mM for its autoxidation products. Similarly, for arachidonic acid and its derivatives, equieffective concentrations were 10, 0.104 and 0.112 mM, respectively. The potency of the autoxidized fatty acid derivatives varied with both duration of autoxidation and the specific structure. Methyloleate and oleyl alcohol remained inactive even after a prolonged oxidation, whereas methyllinoleate and linoleyl alcohol were very potent only after 4 weeks but not after 1 week autoxidation. The potency of esters and alcohols with three or more double bonds increased significantly even after a short-term autoxidation, reflecting the differences in both the rate of formation and the contribution to calcium-transporting properties of the primary and secondary oxidation products. All phospholipids tested, with the exception of phosphatidylcholine and lysophosphatidylcholine, showed considerable calcium-transporting activities at 0.01 mM or greater concentrations; some members were of similar or greater potencies than the classical calcium ionophores, X537A and A23187.

Prostaglandins and the mechanism of action of anti-inflammatory drugs

Aspirin and a large number of nonsteroidal anti-inflammatory drugs act primarily through the inhibition of prostaglandin synthesis by inhibiting the enzyme cyclooxygenase. Other groups of biologically active polyunsaturated fatty acid derivatives including the leukotrienes, are generally not inhibited by this class of drugs in the same concentration ranges. Inhibition of the vasodilator prostaglandins, prostaglandin E 2 and prostacyclin, as well as the leukotrienes, may reduce their inflammatory effects in several disease states. In addition, prostaglandin synthesis is also inhibited by glucocorticoids even though their mode of action may involve other effects as well. Prostaglandin E 2 stimulates the osteoclastic reabsorption of juxtaarticular bone; its inhibition by nonsteroidal anti-inflammatory agents may, therefore, retard the process of bone erosion in rheumatoid arthritis and in other inflammatory processes. Inhibition of prostaglandin synthesis by these drugs accounts for many of their major toxic effects, including gastritis, which is the most common side effect; precipitation or aggravation of renal failure; fluid retention; hyperkalemia; antiplatelet effects with hemorrhagic phenomena; and aggravation of asthma and rhinosinusitis. Inhibition of prostaglandin synthesis can, therefore, account for most of the therapeutic as well as toxic effects of the nonsteroidal anti-inflammatory agents. Inhibition of pathways of synthesis of other important mediators, such as leukotrienes, are currently under investigation and may provide another approach for the development of new therapeutic agents.

Evidence against a PGF4a prostaglandin structure in trout tissue—A correction

Analysis of the oxygenated products generated from docosahexaenoic acid by trout gill tissue and reinterpretation of the mass spectrum of the proposed novel protanoid indicate that the compounds identified as n-3 prostaglandins are trihydroxylated derivatives of the precursor polyunsaturated fatty acids.

High-performance liquid chromatography of fatty acids: quantitative analysis of saturated, monoenoic, polyenoic and geometrical isomers

A procedure is described for the rapid preparation of phenacyl and naphthacyl derivatives of fatty acids. These derivatives of saturated, monounsaturated, and polyunsaturated fatty acids were analyzed by high-performance liquid chromatography (HPLC) on a C 18 reversed-phase column at nanogram sensitivity. Standard mixtures of fatty acids gave quantitative mole percentages. HPLC analyses of phenacyl and naphthacyl derivatives of fatty acids from several seed oils compared well with values obtained by gas—liquid chromatography (GLC). Oleic and elaidic, geometrical octadecenoate isomers, were well resolved. Three of the four Δ 9,12-octadecadienoic acids, geometrical isomers of linoleic acid, were also resolved. The rapid quantitative analysis of fatty acid phenacyl derivatives by HPLC hold some advantages over GLC, especially with samples that contain heat labile and short-chain fatty acids. Phenacyl derivatives of monoenoic fatty acids were also shown to undergo cis-trans isomerization when exposed to ultraviolet light.

Prostaglandin biochemistry, pharmacy and physiological function. The prostaglandins, thromboxanes and leukotrienes.

The prostaglandins, thromboxanes and leukotrienes constitute a rapidly growing family of compounds, all of which are oxygenated derivatives of certain polyunsaturated fatty acids, such as arachidonic acid. Most of these metabolites are biologically very potent substances, displaying a wide variety of actions in many different biological systems. The prostaglandins were originally discovered in the reproductive tract, though it is now known that most cell types in the body possess the enzymes necessary for their biosynthesis. Due to the ubiquitous occurrence of the prostaglandins and related substances, as well as their strong and diversified biological effects, they are believed to participate in numerous biological processes, physiological as well as pathological. In certain cases such a participation has also been proved: in the reproductive tract, prostaglandins are known to be involved in such events as pregnancy, parturition, dysmenorrhea and luteolysis.

The preparation and characterization of the methoxy derivatives of polyunsaturated fatty acids: Stabilized product analogs of lipoxygenase catalysis

AbstractThe products from the action of soybean lipoxygenase on a series of polyunsaturated fatty acids have been converted in 2 steps into the corresponding methoxy derivatives. The product hydroperoxides were reduced in situ to alcohols with sodium borohydride. The ethers were generated by treatment of the alcohols with sodium hydride and methyl iodide in tetrahydrofuran. 13‐Methoxy‐9(Z),11(E)‐octadecadienoic, 15‐methoxy‐11(Z),13(E)‐eicosadienoic and 15‐methoxy‐5(Z),8(Z),11(Z), 13(E)‐eicosatetraenoic acids were thus prepared. The methyl ethers were analyzed and the structures established by high performance liquid chromatography, nuclear magnetic resonance and infrared spectrometry, polarimetry and mass spectroscopy (as methyl esters). The methylation reaction proceeds without molecular rearrangements or racemiziation.

Adsorptive bleaching and molecular distillation of menhaden oil

AbstractSome of the major barriers to wide acceptance of fish oils as sources of polyunsaturated triglycerides, fatty acids, and fatty acid derivatives have been the problems associated with color, odor, flavor, and other impurities. Adsorptive bleaching and molecular distillation were investigated as methods to obtain natural triglycerides from menhaden oil that do not have undesirable flavors and odors. Results of these studies have shown that certain activated clays will satisfactorily reduce the color of commercial menhaden oil but will not remove the odor and flavor. Molecular distillation was found to be more effective in improving the odor and flavor of the oil than adsorptive bleaching with activated clays but somewhat less effective in reducing the color. When used jointly with bleaching, molecular distillation yields menhaden oil of high quality, suitable for use both in animal and human nutrition and in medical research. Spectral data in the 400舑700 mƁ range were used to evaluate the success of the refining process.