Identification of 8-iso-prostaglandin F(2alpha) in rat brain neuronal endings: a possible marker of membrane phospholipid peroxidation.
Isoprostanes are a family of prostaglandin (PG) F and E isomers generated by free-radical attack from membrane bound arachidonic acid. We measured detectable levels of 8-iso-PGF(2alpha) in the perfusates of synaptosomes obtained from different areas of the rat brain cortex. A small but significant release of this isoprostane was found under basal conditions from all the areas explored; being lower in the dorsal cortex in respect to the frontal, parietal and occipital areas. Exposure of synaptosomes to a phospholipase A(2) activator, i.e. calcium-ionophore A23187, an oxidant agent, such as hydrogen peroxide or amyloid beta-peptide did not modify 8-iso-PGF(2alpha) release when these stimuli were applied separately. However, either hydrogen peroxide or amyloid beta-peptide increased 8-iso-PGF(2alpha) release in a dose-dependent manner, when given in the presence of the calcium-ionophore A23187. Synaptosome treatment with a non-selective cyclooxygenase inhibitor (fenoprofen) did not modify 8-iso-PGF(2alpha) release in any way, but treatment with a water soluble antioxidant (Trolox C) completely suppressed isoprostane release under basal conditions, as well as after the oxidant injury induced either by hydrogen peroxide or amyloid beta-peptide. We conclude that, in neuronal endings, 8-iso-PGF(2alpha) is generated under basal conditions and its formation may be increased in a dose-dependent fashion by oxidant stimuli through a cyclooxygenase-independent mechanism involving free radical-catalyzed oxidation of arachidonic acid on membrane phospholipids.
Brunetti
Luigi
L
Department of Drug Sciences, G. D'Annunzio University, via dei Vestini, 66013, Chieti, Italy. brunetti@unich.it
Orlando
Giustino
G
Michelotto
Barbara
B
Recinella
Lucia
L
Di Nisio
Chiara
C
Ciabattoni
Giovanni
G
Vacca
Michele
M
D016229:Amyloid beta-Peptides / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002839:Chromans / Q000494:pharmacology; D015237:Dinoprost / Q000031:analogs & derivatives*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D028441:F2-Isoprostanes / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008297:Male; D009411:Nerve Endings / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D016229:Amyloid beta-Peptides; D002839:Chromans; D004791:Enzyme Inhibitors; D028441:F2-Isoprostanes; C075750:8-epi-prostaglandin F2alpha; D000001:Calcimycin; D015237:Dinoprost; D006861:Hydrogen Peroxide; D010741:Phospholipases A; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid