15-deoxy-delta(12-14)-prostaglandin-j2 and 4-hydroxy-2-nonenal

There is increasing evidence to suggest that reactive oxygen species, including a variety of lipid oxidation products and other physiologically existing oxidative stimuli, can induce an adaptive response and enhance cell tolerance. In the present study, by using cultured cortical neurons, we investigated the effect of electrophilic lipids, such as 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) and 4-hydroxy-2-nonenal (4-HNE) against the cell death induced by H(2)O(2) and glutamate. Pre-treatment with both 15d-PGJ(2) and 4-HNE at sublethal concentrations resulted in a significant protective effect against oxidative stress, and 15d-PGJ(2), in particular, exhibited a complete protective effect against glutamate-induced neuronal cell death. Pre-treatment with 15d-PGJ(2) increased the intracellular glutathione (GSH) as well as the gene expression of glutamate-cysteine ligase (GCL), the rate-limiting enzyme of GSH synthesis. 15d-PGJ(2) protected cells from glutamate-induced GSH depletion, while the inhibition of cellular GSH synthesis by buthionine sulfoximine abolished the adaptive response induced by 15d-PGJ(2). These findings indicate that at low levels, 15d-PGJ(2) acts as a potent survival mediator against glutamate-induced insults via the induction of an adaptive response primarily through the up-regulation of the intracellular GSH synthesis.

Topics: Aldehydes; Animals; Buthionine Sulfoximine; Cell Death; Cells, Cultured; Cerebral Cortex; Cysteine Proteinase Inhibitors; Dose-Response Relationship, Drug; Embryo, Mammalian; Enzyme Inhibitors; Glutamic Acid; Glutathione; Immunologic Factors; Neurons; Prostaglandin D2; Rats; Time Factors; Up-Regulation

The molecular mechanisms through which oxidized lipids and their electrophilic decomposition products mediate redox cell signalling is not well understood and may involve direct modification of signal-transduction proteins or the secondary production of reactive oxygen or nitrogen species in the cell. Critical in the adaptation of cells to oxidative stress, including exposure to subtoxic concentrations of oxidized lipids, is the transcriptional regulation of antioxidant enzymes, many of which are controlled by antioxidant-responsive elements (AREs), also known as electrophile-responsive elements. The central regulator of the ARE response is the transcription factor Nrf2 (NF-E2-related factor 2), which on stimulation dissociates from its cytoplasmic inhibitor Keap1, translocates to the nucleus and transactivates ARE-dependent genes. We hypothesized that electrophilic lipids are capable of activating ARE through thiol modification of Keap1 and we have tested this concept in an intact cell system using induction of glutathione synthesis by the cyclopentenone prostaglandin, 15-deoxy-Delta12,14-prostaglandin J2. On exposure to 15-deoxy-Delta12,14-prostaglandin J2, the dissociation of Nrf2 from Keap1 occurred and this was dependent on the modification of thiols in Keap1. This mechanism appears to encompass other electrophilic lipids, since 15-A(2t)-isoprostane and the lipid aldehyde 4-hydroxynonenal were also shown to modify Keap1 and activate ARE. We propose that activation of ARE through this mechanism will have a major impact on inflammatory situations such as atherosclerosis, in which both enzymic as well as non-enzymic formation of electrophilic lipid oxidation products are increased.

Topics: Aldehydes; Antioxidants; Base Sequence; Carrier Proteins; Cell Line; Cysteine; DNA-Binding Proteins; Glutamate-Cysteine Ligase; Glutathione; Humans; Molecular Sequence Data; Mutation; NF-E2-Related Factor 2; Oxidation-Reduction; Oxidative Stress; Prostaglandin D2; Prostaglandins A; Response Elements; Signal Transduction; Trans-Activators; Transcriptional Activation

The retina, which is exposed to both sunlight and very high levels of oxygen, is exceptionally rich in polyunsaturated fatty acids, which makes it a favorable environment for the generation of reactive oxygen species. The cytotoxic effects of hydrogen peroxide (H2O2) induced oxidative stress on retinal pigment epithelium were characterized in this study.. The MTT cell viability assay, Texas-Red phalloidin staining, immunohistochemistry and Western blot analysis were used to assess the effects of oxidative stress on primary human retinal pigment epithelial cell cultures and the ARPE-19 cell line.. The treatment of retinal pigment epithelial cells with H2O2 caused a dose-dependent decrease of cellular viability, which was preceded by a significant cytoskeletal rearrangement, activation of the Extracellular signal-Regulated Kinase, lipid peroxidation and nuclear condensation. This cell death was prevented partially by the prostaglandin derivative, 15d-PGJ2 and by the protein kinase inhibitor, AG126.. 15d-PGJ2 and AG126 may be useful pharmacological tools in the future capable of preventing oxidative stress induced RPE cell death in human ocular diseases.

Topics: Actins; Aldehydes; Blotting, Western; Cell Death; Cell Survival; Cells, Cultured; Dose-Response Relationship, Drug; Enzyme Inhibitors; Fluorescent Antibody Technique, Indirect; Humans; Hydrogen Peroxide; Immunoenzyme Techniques; Immunologic Factors; Lipid Peroxidation; Mitogen-Activated Protein Kinases; Oxidative Stress; Phosphorylation; Pigment Epithelium of Eye; Prostaglandin D2; Protein-Tyrosine Kinases; Receptors, Cytoplasmic and Nuclear; Transcription Factors; Tyrphostins

The lipid products derived from the cyclooxygenase pathway can have diverse and often contrasting effects on vascular cell function. Cyclopentenone prostaglandins (cyPGs), such as 15-deoxy-Delta(12,14)-prostaglandin-J(2) (15d-PGJ(2)), a peroxisome proliferator-activated receptor-gamma (PPARgamma) agonist, have been reported to cause endothelial cell apoptosis, yet in other cell types, cyPGs induce cytoprotective mediators, such as heat shock proteins, heme oxygenase-1, and glutathione (GSH). Herein, we show in human endothelial cells that low micromolar concentrations of 15d-PGJ(2) enhance GSH-dependent cytoprotection through the upregulation of glutamate-cysteine ligase, the rate-limiting enzyme of GSH synthesis, as well as GSH reductase. The effect of 15d-PGJ(2) on GSH synthesis is attributable to the cyPG structure but is independent of PPAR, inasmuch as the other cyPGs, but not PPARgamma or PPARalpha agonists, are able to increase GSH. The increase in cellular GSH is accompanied by abrogation of the proapoptotic effects of 4-hydroxynonenal, a product of lipid peroxidation present in atherosclerotic lesions. However, higher concentrations of 15d-PGJ(2) (10 micromol/L) cause endothelial cell apoptosis, which is further enhanced by depletion of cellular GSH by buthionine sulfoximine. We propose that the GSH-dependent cytoprotective pathways induced by 15d-PGJ(2) contribute to its antiatherogenic effects and that these pathways are distinct from those leading to apoptosis.

Topics: Aldehydes; Apoptosis; Arachidonic Acid; Cell Survival; Cells, Cultured; Dose-Response Relationship, Drug; Endothelium, Vascular; Glutamate-Cysteine Ligase; Glutathione; Humans; Kinetics; Prostaglandin D2; Prostaglandins; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; Transcription Factors