Changes of free fatty acids and acyl-CoAs in rat brain hippocampal slice with tetraethylammonium-induced long-term potentiation

We investigated the role of acyl-CoAs during induction and maintenance of long-term potentiation in rat brain hippocampus. Changes of acyl-CoA and free fatty acids (FFA) in hippocampus were measured during tetraethylammonium (TEA)-induced LTP. Results indicated that concentrations of acyl-CoAs and FFAs in slices were changed during TEA-induced LTP and 16:0-CoA and 18:0-CoA were increased in the early phase of stimulation, whereas free fatty acids in this phase were rather decreased. The increase of 20:4-CoA was delayed more than saturated acyl-CoAs. To examine the role of acyl-CoA in LTP of evoked transmitter release, we measured the glutamate release from hippocampal slice with the addition of acyl-CoA using glutamate electrode. Acyl-CoA (16:0-, 18:1-, and 20:4-CoA) could enhance glutamate release in hippocampal slice. It is suggested that saturated acyl-CoAs may play a functional role in the early phase of LTP.     

The use of Pseudomonas acyl-CoA synthetase to form acyl-CoAs from dicarboxylic fatty acids

Pseudomonas acyl-CoA synthetase is shown to act on saturated dicarboxylic acids with a chain length of C10 or greater to produce conjugates containing a single CoA unit. The synthetase can, therefore, be used to generate novel acyl-CoA analogues for studies on proteins that utilise, bind to, or are modulated by acyl-CoAs.     

Proinflammatory properties of unsaturated fatty acids and their monohydroxy metabolites

The proinflammatory effects of unsaturated fatty acids and, where appropriate, their monohydroxy derivatives, have been investigated both by application to human skin and with respect to human polymorphonuclear leukocyte (PMN) migration. Of the fatty acids applied to the skin only eicosapentaenoic and arachidonic acids (EPA;AA) produced consistent, measurable erythema. The monohydroxy derivatives of the two fatty acids also caused erythema. the 12-hydroxy isomers being the most potent. Chemokinetic activity towards PMNs was observed in the presence of AA, EPA and α-linolenic acid using an agarose microdroplet chemokinesis assay. In contrast to their properties, the 5-hydroxy isomers of AA and EPA were the most potent, being approximately 10 times more chemokinetically active than the other isomers. Quantification of the hydroxyeicosatetraenoic and hydroxyeicosapentaenoic acids (HETEs;HEPEs) in the lesional skin of psoriatic patients demonstrated that, of the metabolites measured, 12-HETE was present in the greatest amounts. Twenty five times more 12-HETE than 12- or 15-HEPE was detected, these being the most abundant of teh HEPEs formed. The monohydroxy derivatives of AA and EPA may contribute to the inflammatory changes observed in psoriasis. The HETEs appear to be of greater importance than the HEPEs in view of the relative amounts present.     

Proinflammatory properties of unsaturated fatty acids and their monohydroxy metabolites

The proinflammatory effects of unsaturated fatty acids and, where appropriate, their monohydroxy derivatives, have been investigated both by application to human skin and with respect to human polymorphonuclear leukocyte (PMN) migration. Of the fatty acids applied to the skin only eicosapentaenoic and arachidonic acids (EPA; AA) produced consistent, measurable erythema. The monohydroxy derivatives of the two fatty acids also caused erythema, the 12-hydroxy isomers being the most potent. Chemokinetic activity towards PMNs was observed in the presence of AA, EPA and alpha-linolenic acid using an agarose microdroplet chemokinesis assay. In contrast to their in vivo properties, the 5-hydroxy isomers of AA and EPA were the most potent, being approximately 10 times more chemokinetically active than the other isomers. Quantification of the hydroxyeicosatetraenoic and hydroxyeicosapentaenoic acids (HETEs; HEPEs) in the lesional skin of psoriatic patients demonstrated that, of the metabolites measured, 12-HETE was present in the greatest amounts. Twenty five times more 12-HETE than 12- or 15-HEPE was detected, these being the most abundant of the HEPEs formed. The monohydroxy derivatives of AA and EPA may contribute to the inflammatory changes observed in psoriasis. The HETEs appear to be of greater importance than the HEPEs in view of the relative amounts present.     

Interaction of free fatty acids with mitochondria during uncoupling of oxidative phosphorylation

The activity of free saturated fatty acids (caprylic, capric, lauric, myristic, palmitic and stearic) as inducers and regulators of uncoupling of oxidative phosphorylation with participation of ADP/ATP antiporter, aspartate/glutamate antiporter and cyclosporin A-sensitive structure was investigated in experiments on rat liver mitochondria. It is established that at equal uncoupling activity of fatty acids the regulatory effect is minimal for caprylic acid and raised with increasing the hydrophobicity of fatty acids reaching the maximum value for stearic acid. There exists the linear dependence of the regulatory effect value of fatty acids on fatty acids content in the hydrophobic region of the inner membrane. The model that describes the interaction of fatty acids with the hydrophobic region of the mitochondrial inner membrane preserving functional activity of organelles is developed. It is established that if molecules of various fatty acids being in the hydrophobic region of the membrane are equally effective as uncoupling regulators, their specific uncoupling activity is different. Caprylic acid, a short-chain fatty acid, possesses the highest uncoupling activity. As the acyl chain length increases, the specific uncoupling activity of fatty acids reduces exponentially. Under these conditions components of the uncoupling activity sensitive to glutamate and carboxyatractylate and glutamate and insensitive to these reagents (but sensitive to cyclosporin A) change approximately equally.     

Essential fatty acids and their metabolites in signal transduction.

The above examples argue that the diversity of eicosanoid structures is reflected in distinct actions, that the membrane-permeable nature of these molecules provides a system for interactive cellular signalling that may be particularly important in the nervous system, and that convincing evidence exists for direct actions of eicosanoids on both ion channels and kinases, as well as G-protein-coupled receptors.     

Interaction of inorganic mercury with CoA-SH and acyl-CoAs

Sulfur containing biomolecules are involved in complexes with mercury. CoA is an important cofactor for many enzymes involved in metabolic processes. Fatty acyl-CoA-thioesters, substrates of mitochondrial ß-oxidation, are sulfur containing compounds and potential mercury ligands. The CoA-Hg²⁺ complex can be easily assessed by UV-Vis spectroscopy or indirectly by antibacterial tests that reconfirmed the protective role of CoA on E. coli. The characteristics of these complexes were determined by means of FTIR spectroscopy. The reverse phase liquid chromatography combined with electrospray ionization tandem mass spectrometry was used for detection of the side-product that resulted through the cleavage of thioesters in the presence of mercury. An unexpected result was the detection of octathioic acid as a product. Our study shows that mitochondrial β-oxidation can be affected by thioesters depletion assisted by Hg²⁺. The GC-MS technique could be used to detect some possible mitochondrial injuries due to the heavy metal ions.     

Interaction of alpha-tocopherol with free fatty acids. Spatial organization of the complex

Stereoconfiguration of alpha-tocopherol-linoleic acid complex was studied using high resolution IH-NMR-spectroscopy. The addition of a fatty acid (linoleate) to alpha-tocopherol solution in CDCl3 resulted in the broadening of IH-NMR lines for OH- and phe-CH3-alpha-tocopherol groups. No changes in chemical shift values of IH-NMR lines for linoleic acid were observed after the addition of alpha-tocopherol to linoleic acid solution in CDCl3. It is concluded that in the complexes formed linoleic acid is located in the phenolic ring plane of alpha-tocopherol. The conclusion is supported by the data obtained on molecular models.     

Interaction of free fatty acids with mitochondria: coupling, uncoupling and permeability transition

Long chain free fatty acids (FFA) exert, according to their actual concentration, different effects on the energy conserving system of mitochondria. Sub-micromolar concentrations of arachidonic acid (AA) rescue DeltapH-dependent depression of the proton pumping activity of the bc1 complex. This effect appears to be due to a direct interaction of AA with the proton-input mouth of the pump. At micromolar concentrations FFA increase the proton conductance of the inner membrane acting as protonophores. FFA can act as natural uncouplers, causing a mild uncoupling, which prevents reactive oxygen species production in the respiratory resting state. When Ca(2+)-loaded mitochondria are exposed to micromolar concentrations of FFA, the permeability of the inner membrane increases, resulting in matrix swelling, rupture of the outer membrane and release of intermembrane pro-apoptotic proteins. The characteristics of AA-induced swelling appear markedly different in mitochondria isolated from heart or liver. While in the latter it presents the canonical features of the classical permeability transition (PT), in heart mitochondria substantial differences are observed concerning CsA sensitivity, DeltaPsi dependence, reversibility by BSA and specificity for the activating divalent cation. In heart mitochondria, the AA-dependent increase of the inner membrane permeability is affected by ANT ligands such as adenine nucleotides and atractyloside. AA apparently causes a Ca2+-mediated conversion of ANT from a translocator to a channel system. Upon diamide treatment of heart mitochondria, the Ca2+/AA-induced CsA insensitive channel is converted into the classical PT pore. The relevance of these observations in terms of tissue-specific components of the putative PTP and heart ischemic and post-ischemic process is discussed.     

Interaction of rat liver microsomes containing saturated or unsaturated fatty acids with fatty acid binding protein: Peroxidation effect

In the studies described here rat liver microsomes containing labeled palmitic, stearic, oleic or linoleic acids were incubated with fatty acid binding protein (FABP) and the rate of removal of¹⁴C-labeled fatty acids from the membrane by the soluble protein was measured using a model system. More unsaturated than saturated fatty acids were removed from native liver microsomes incubated with similar amounts of FABP. Thein vitro peroxidation of microsomal membranes mediated by ascorbate-Fe⁺⁺, modified its fatty acid composition with a considerable decrease of the peroxidizability index. These changes in the microsomes facilitated the removal of oleic and linoeic acids by FABP, but the removal of palmitic and stearic acids was not modified. This effect is proposed to result from a perturbation of membrane structure following peroxidation with release of free fatty acids from susceptible domains.Abbreviations BSA bovine serum albumin - FABP fatty acid binding protein     

Interaction between free fatty acids and Ca2+-dependent ATPase from sarcoplasmic reticulum membranes

The interaction between free fatty acids and Ca2+-dependent ATPase, an intrinsic protein of sarcoplasmic reticulum membranes, was studied with relevance to the changes in membrane permeability induced by free fatty acids. It was found that only unsaturated fatty acids increase the permeability of reticulum membranes for Ca2+, this effect being completely reversible. The increase in the membrane permeability by fatty acids is coupled to a generation of a channel for Ca2+ efflux under effect of Ca2+-dependent ATPase. The interaction between fatty acids and Ca2+-dependent ATPase was demonstrated by the protein fluorescence and electron paramagnetic resonance methods, using spin-labelled fatty acid derivatives. A model demonstrating the increase of sarcoplasmic reticulum membrane permeability for Ca2+ in the presence of the fatty acid-Ca2+-dependent ATPase complex is proposed.     

Interaction of fatty acids with beta-lactoglobulin and albumin from ruminant milk

beta-Lactoglobulin isolated from milk of cow, sheep, and goat had about 0.5 mol of fatty acids bound per mol of monomer protein. Fatty acids, mainly palmitic and oleic acids, were the major components (about 75% of total lipids). Albumin isolated from the same samples had about 4.5 mol of fatty acids bound per mol of protein. These two proteins were the only whey proteins able to bind labeled fatty acids in vitro. Interaction of beta-lactoglobulin and albumin with insolubilized fatty acids showed some differences, suggesting different structures of the respective fatty acid binding sites.     

Interaction of fatty acids with lipid bilayers

We present a method by which it is possible to describe the binding of fatty acids to phospholipid bilayers. Binding constants for oleic acid and a number of fatty acids used as spectroscopic probes are deduced from electrophoresis measurements. There is a large shift in $\text{p}\text{K}$ value for the fatty acids on binding to the phospholipid bilayers, consistent with stronger binding of the uncharged form of the fatty acid. For dansylundecanoic acid, fluorescence titrations are consistent with the binding constants derived from the electrophoresis experiments. For 12-(9-anthroyloxy)stearic acid, fluorescence and electrophoresis data are inconsistent, and we attribute this to quenching of fluorescence at high molar ratios of 12-anthroylstearic acid to phospholipid in the bilayer.     

Apolipoprotein C-I binds free fatty acids and reduces their intracellular esterification

Mice that overexpress human apolipoprotein C-I (apoC-I) homozygously (APOC1(+/+) mice) are protected against obesity and show cutaneous abnormalities. Although these effects can result from our previous observation that apoC-I inhibits FFA generation by LPL, we have also found that apoC-I impairs the uptake of a FFA analog in adipose tissue. In this study, we tested the hypothesis that apoC-I interferes with cellular FFA uptake independent of LPL activity. The cutaneous abnormalities of APOC1(+/+) mice were not affected after transplantation to wild-type mice, indicating that locally produced apoC-I prevents lipid entry into the skin. Subsequent in vitro studies with apoC-I-deficient versus wild-type macrophages revealed that apoC-I reduced the cell association and subsequent esterification of [(3)H]oleic acid by approximately 35% (P < 0.05). We speculated that apoC-I binds FFA extracellularly, thereby preventing cell association of FFA. We showed that apoC-I was indeed able to mediate the binding of oleic acid to otherwise protein-free VLDL-like emulsion particles involving electrostatic interaction. We conclude that apoC-I binds FFA in the circulation, thereby reducing the availability of FFA for uptake by cells. This mechanism can serve as an additional mechanism behind the resistance to obesity and the cutaneous abnormalities of APOC1(+/+) mice.     

Interaction of alpha-tocopherol with free fatty acids. Mechanism of stabilization of lipid bilayer microviscosity

Using ESR-spin probes and 1H-NMR-spectroscopy methods the effect of alpha-tocopherol on liposome microviscosity has been studied. alpha-Tocopherol has been shown to remove the chaotropic action of free fatty acids on bilayer. The stabilization effect found has a common nature and does not depend on the chemical structure of the phopsholipid functional polar groups, the unsaturation degree of free fatty acids as well as fatty acids residua entering into phospholipid composition. Analog of alpha-tocopherol without phytol chain 2,2,5,7,8-penthamethyl-6-oxychroman does not show the stabilizing effect on the microviscosity of lipid bilayer under the action of free fatty acids. It indicates that both chromanol nucleus and phytol chain of alpha-tocopherol molecule are necessary for stabilizing action. The data obtained allow to suppose that the interaction of alpha-tocopherol with free fatty acids may be one of the molecular mechanisms of lipid bilayer microvicosity stabilization.     

Interaction of free fatty acids with the erythrocyte membrane as affected by hyperthermia and ionizing radiation

The interference of hyperthermia and ionizing radiation, respectively, with the effects of capric (100), lauric (120), myristic (140), oleic (cis-181) and elaidic (trans-181) acids on the osmotic resistance of human erythrocytes was investigated. The results are summarized as follows: (A) not only at 37°, but also at 42° and 47°C lauric acid (120) represents the minimum chain length for the biphasic behaviour of protecting against hypotonic hemolysis at a certain lower concentration range and hemolysis promotion at subsequent higher concentrations; (B) with increasing temperatures the protecting as well as the hemolytic effects occur at lower concentrations of the fatty acids; (C) the increase of temperature promotes the extent of hemolysis and reduces the extent of protection against hypotonic hemolysis; (D) Gamma-irradiation of erythrocytes selectively affects the concentration of oleic acid at which maximum protection against hypotonic hemolysis occurs, without altering the minimum concentration for 100% hemolysis.