linoleic-acid and leukotoxin

Linoleic acid (LA) is the most abundant polyunsaturated fatty acid found in the Western diet. Cytochrome P450-derived LA metabolites 9,10-epoxyoctadecenoic acid (9,10-EpOME), 12,13-epoxyoctadecenoic acid (12,13-EpOME), 9,10-dihydroxy-12Z-octadecenoic acid (9,10-DiHOME) and 12,13-dihydroxy-9Z-octadecenoic acid (12,13-DiHOME) have been studied for their association with various disease states and biological functions. Previous studies of the EpOMEs and DiHOMEs have focused on their roles in cytotoxic processes, primarily in the inhibition of the neutrophil respiratory burst. More recent research has suggested the DiHOMEs may be important lipid mediators in pain perception, altered immune response and brown adipose tissue activation by cold and exercise. The purpose of this review is to summarize the current understanding of the physiological and pathophysiological roles and modes of action of the EpOMEs and DiHOMEs in health and disease.

Topics: Adipose Tissue, Brown; Analgesics; Animals; Cytochrome P-450 Enzyme System; Endocrine System; Epoxide Hydrolases; Exotoxins; Humans; Immune System; Inflammation; Linoleic Acid; Lipids; Lung; Mice; Neutrophils; Oleic Acids; Oxidation-Reduction; Pain Management; Respiratory Burst; Stearic Acids

Polyunsaturated fatty acids such as linoleic acid are well known dietary lipids that may be atherogenic by activating vascular endothelial cells. In the liver, fatty acids can be metabolized by cytochrome P450 (CYP) enzymes, but little is known about the role of these enzymes in the vascular endothelium. CYP 2C9 is involved in linoleic acid epoxygenation, and the major product of this reaction is leukotoxin (LTX). We investigated the role of CYP-mediated mechanisms of linoleic acid metabolism in endothelial cell activation by examining the effects of linoleic acid or its oxidized metabolites such as LTX and leukotoxin diol (LTD).. The effect of linoleic acid on CYP 2C9 gene expression was studied by RT-PCR. Oxidative stress was monitored by measuring DCF fluorescence and intracellular glutathione levels, and electrophoretic mobility shift assay was carried out to study the activation of oxidative stress sensitive transcription factors. Analysis of oxidized lipids was carried out by liquid chromatography/mass spectrometry.. Linoleic acid treatment for six hours increased the expression of CYP 2C9 in endothelial cells. Linoleic acid-mediated increase in oxidative stress and activation of AP-1 were blocked by sulfaphenazole, a specific inhibitor of CYP 2C9. The linoleic acid metabolites LTX and LTD increased oxidative stress and activation of transcription factors only at high concentrations.. Our data show that CYP 2C9 plays a key role in linoleic acid-induced oxidative stress and subsequent proinflammatory events in vascular endothelial cells by possibly causing superoxide generation through uncoupling processes.

Topics: Animals; Aryl Hydrocarbon Hydroxylases; Cytochrome P-450 CYP2C9; Dose-Response Relationship, Immunologic; Electrophoretic Mobility Shift Assay; Endothelial Cells; Endothelium, Vascular; Exotoxins; Gas Chromatography-Mass Spectrometry; Gene Expression Regulation; Glutathione; Humans; Immunosuppressive Agents; Inflammation Mediators; Linoleic Acid; NF-kappa B; Oxidative Stress; Pulmonary Artery; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; Stearic Acids; Swine; Transcription Factor AP-1; Umbilical Veins

Hemoproteins are known to have quasilipoxygenase activity that converts linoleic acid (LA) to its hydroperoxides. However, it is not still clear whether, like lipoxygenases, hemoproteins can produce LA hydroperoxides when the LA is part of a mixture containing many different saturated and unsaturated fatty acids. In this study, we found that such hemoprotein as cytochrome c (Cyt c) did not produce LA hydroperoxides from the phospholipase A(2) (PL-A(2)) hydrolysis products of egg yolk phosphatidylcholine (PC). We also found that traces of hydroperoxides and a high concentration of the target unsaturated fatty acid (LA) needs to be present in a fatty acid mixture before the quasi-lipoxygenase activity of Cyt c becomes apparent. We also attempted to elucidate how Cyt c interact with porcine leukocyte 12-lipoxygenase (12-LOX). Hemoproteins are known to possess pseudo-lipohydroperoxidase activity, and can remove the hydroperoxides of unsaturated fatty acids from a reaction mixture. However, we found that Cyt c catalyzed the reaction by which hydroperoxides degrade LA, and thus enhanced the LA-degrading activity of 12-LOX. This hemoprotein-induced promotion of the ability of 12-LOX to degrade LA was observed even when the reaction mixture contained many different saturated and unsaturated fatty acids.

Topics: Animals; Arachidonate 12-Lipoxygenase; Cardiolipins; Cytochrome c Group; Exotoxins; Glutathione Peroxidase; Leukocytes; Linoleic Acid; Lipid Peroxides; Myoglobin; Phosphatidylcholines; Phospholipases A; Swine

Leukotoxin (Lx), an epoxide derivative of linoleic acid, has been suggested to be a toxic mediator of multiple organ failure in burn patients and of acute respiratory distress syndrome. Lx production was recently shown during myocardial ischemia/reperfusion. However, a recent study suggested that to be toxic Lx must be metabolized to Lx-diol. In the present study, isolated adult rat ventricular myocytes were studied with the whole-cell patch-clamp technique to determine the effects of these compounds on cardiac electrical activity. Measurements of action potentials showed that neither linoleic acid nor Lx (100 microM) caused any significant changes in action potential properties. However, Lx-diol in the range of 10-100 microM produced a dose dependent increase in duration and a decrease in overshoot of the action potential. Subsequent voltage clamp experiments isolating Na current (INa) and transient outward K current (Ito) revealed that Lx-diol inhibited INa and Ito by about 80% at 100 microM, while linoleic acid and Lx had no effect on these currents at the same concentration. While Lx-diol produced the same inhibition of INa and Ito at 100 microM, its effects were more potent on Ito with significant inhibition at 10 microM. Lx-diol also hastened the activation kinetics of Ito but not INa. The action of Lx-diol was rapid (reaching steady state in 3-5 min) and was reversible in 5-10 min following washout. Thus, Lx-diol could favor arrhythmias or cardiac arrest in intact heart and may be responsible for the cardiac problems seen in systemic inflammatory response syndrome. These results further support the suggestion that Lx is not toxic in the heart but rather must be metabolized to Lx-diol to produce toxic effects on cardiac muscle.

Topics: Action Potentials; Animals; Arrhythmias, Cardiac; Cells, Cultured; Dose-Response Relationship, Drug; Exotoxins; Heart Ventricles; Linoleic Acid; Mass Spectrometry; Myocardium; Patch-Clamp Techniques; Potassium; Rats; Sodium; Stearic Acids

We found that cytochrome c (Cyt c) could oxidize cardiolipin (CL), and detected monoepoxides of linoleic acid (LA) in the fatty acids constituting the oxidized CL. We also found that in the presence of CL and Cyt c, free LA was oxidized and LA monoepoxides were produced. The aim of this study was to elucidate the mechanism of this lipid peroxidation. We concluded that ferric Cyt c produced some radical species from water-soluble oxygen in the presence of CL (CL-Cyt c system) and that radicals oxidized free LA or CL. The CL-Cyt c system may be another LA monoepoxide producing system in the neutrophil and may account for the lipid peroxidation observed in the ischemia-reperfusion-induced cardiac injury.

Topics: Cardiolipins; Chromatography, High Pressure Liquid; Cytochrome c Group; Epoxy Compounds; Exotoxins; Ferrous Compounds; Gas Chromatography-Mass Spectrometry; Linoleic Acid; Linoleic Acids; Lipid Peroxides; Oxidation-Reduction; Reperfusion Injury; Spectrum Analysis

Some monoepoxides of linoleic acid (LA) were converted to monochlorohydrins in low-pH solutions containing chloride ions (Cl-). Conversely, monochlorohydrins of LA were converted to monoepoxides in high-pH solutions. We attempted to determine whether these monochlorohydrins and monoepoxides were produced from LA by the cytochrome-c-H2O2-and/or myeloperoxidase-H2O2-system. The existence of monoepoxides and monochlorohydrins of LA in leukocytes was confirmed by high-performance liquid chromatography (HPLC). Furthermore, leukotoxin in human leukemia cells (THP-1) was stained immunohistochemically by a monoclonal anti-leukotoxin antibody.

Topics: Animals; Cell Line; Chlorohydrins; Chromatography, High Pressure Liquid; Cytochrome c Group; Epoxy Compounds; Exotoxins; Exudates and Transudates; Humans; Hydrogen Peroxide; Hydrogen-Ion Concentration; Leukemia; Leukocytes; Linoleic Acid; Linoleic Acids; Male; Mass Spectrometry; Peroxidase; Rats; Rats, Sprague-Dawley; Tumor Cells, Cultured