Formation of Highly Reactive A-ring and J-ring Isoprostane-like Compounds (A4/J4-neuroprostanes) in Vivo from Docosahexaenoic Acid

Abstract

Free radical-initiated oxidant injury and lipid peroxidation have been implicated in a number of neural disorders. Docosahexaenoic acid is the most abundant unsaturated fatty acid in the central nervous system. We have shown previously that this 22-carbon fatty acid can yield, upon oxidation, isoprostane-like compounds termed neuroprostanes, with E/D-type prostane rings (E4/D4-neuroprostanes). Eicosanoids with E/D-type prostane rings are unstable and dehydrate to cyclopentenone-containing compounds possessing A-type and J-type prostane rings, respectively. We thus explored whether cyclopentenone neuroprostanes (A4/J4-neuroprostanes) are formed from the dehydration of E4/D4-neuroprostanes. Indeed, oxidation of docosahexaenoic acid in vitro increased levels of putative A4/J4-neuroprostanes 64-fold from 88 ± 43 to 5463 ± 2579 ng/mg docosahexaenoic acid. Chemical approaches and liquid chromatography/electrospray ionization tandem mass spectrometry definitively identified them as A4/J4-neuroprostanes. We subsequently showed these compounds are formed in significant amounts from a biological source, rat brain synaptosomes. A4/J4-neuroprostanes increased 13-fold, from a basal level of 89 ± 72 ng/mg protein to 1187 ± 217 ng/mg (n = 4), upon oxidation. We also detected these compounds in very large amounts in fresh brain tissue from rats at levels of 97 ± 25 ng/g brain tissue (n = 3) and from humans at levels of 98 ± 26 ng/g brain tissue (n = 5), quantities that are nearly an order of magnitude higher than other classes of neuroprostanes. Because of the fact that A4/J4-neuroprostanes contain highly reactive cyclopentenone ring structures, it would be predicted that they readily undergo Michael addition with glutathione and adduct covalently to proteins. Indeed, incubation of A4/J4-neuroprostanes in vitro with excess glutathione resulted in the formation of large amounts of adducts. Thus, these studies have identified novel, highly reactive A/J-ring isoprostane-like compounds that are derived from docosahexaenoic acid in vivo. Free radical-initiated oxidant injury and lipid peroxidation have been implicated in a number of neural disorders. Docosahexaenoic acid is the most abundant unsaturated fatty acid in the central nervous system. We have shown previously that this 22-carbon fatty acid can yield, upon oxidation, isoprostane-like compounds termed neuroprostanes, with E/D-type prostane rings (E4/D4-neuroprostanes). Eicosanoids with E/D-type prostane rings are unstable and dehydrate to cyclopentenone-containing compounds possessing A-type and J-type prostane rings, respectively. We thus explored whether cyclopentenone neuroprostanes (A4/J4-neuroprostanes) are formed from the dehydration of E4/D4-neuroprostanes. Indeed, oxidation of docosahexaenoic acid in vitro increased levels of putative A4/J4-neuroprostanes 64-fold from 88 ± 43 to 5463 ± 2579 ng/mg docosahexaenoic acid. Chemical approaches and liquid chromatography/electrospray ionization tandem mass spectrometry definitively identified them as A4/J4-neuroprostanes. We subsequently showed these compounds are formed in significant amounts from a biological source, rat brain synaptosomes. A4/J4-neuroprostanes increased 13-fold, from a basal level of 89 ± 72 ng/mg protein to 1187 ± 217 ng/mg (n = 4), upon oxidation. We also detected these compounds in very large amounts in fresh brain tissue from rats at levels of 97 ± 25 ng/g brain tissue (n = 3) and from humans at levels of 98 ± 26 ng/g brain tissue (n = 5), quantities that are nearly an order of magnitude higher than other classes of neuroprostanes. Because of the fact that A4/J4-neuroprostanes contain highly reactive cyclopentenone ring structures, it would be predicted that they readily undergo Michael addition with glutathione and adduct covalently to proteins. Indeed, incubation of A4/J4-neuroprostanes in vitro with excess glutathione resulted in the formation of large amounts of adducts. Thus, these studies have identified novel, highly reactive A/J-ring isoprostane-like compounds that are derived from docosahexaenoic acid in vivo. docosahexaenoic acid isoprostane neuroprostane prostaglandin 2,2′-azobis(2-amidinopropane) hydrochloride pentafluorobenzyl gas chromatography negative ion chemical ionization mass spectrometry high performance liquid chromatography liquid chromatography electrospray ionization collision-induced dissociation trimethylsilyl methylt-butyl ether N,O-bis(trimethylsilyl)trifluoroacetamide Docosahexaenoic acid (C22:6ω3, DHA)1 is estimated to account for ∼30% of the total fatty acids in brain tissue aminophospholipids (1Skinner E.R. Watt C. Besson J.A.O. Best P.V. Brain. 1993; 116: 717-725Crossref PubMed Scopus (117) Google Scholar, 2Carlson S.E. Semin. Neonatol. 2001; 5: 437-449Abstract Full Text PDF Scopus (107) Google Scholar). DHA is believed to be important for brain development (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar), and its deficiency is associated with abnormalities in brain function (4Conner W.E. Neuringer M. Reisbick S. Nutr. Rev. 1992; 50: 21-29Crossref Scopus (211) Google Scholar). Oxidation of DHA has been an area of intense research because lipid peroxidation has been implicated in the pathogenesis of various central nervous system diseases, among them neurodegenerative disorders including Alzheimer's disease (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar,5Halliwell B. Gutteridge J.M.C. Methods Enzymol. 1990; 186: 1-85Crossref PubMed Scopus (4428) Google Scholar, 6Markesbery W.R. Free Radic. Biol. Med. 1997; 23: 134-147Crossref PubMed Scopus (1966) Google Scholar, 7Knight J.A. Ann. Clin. Lab. Sci. 1997; 27: 11-25PubMed Google Scholar, 8Simonian N.A. Doyle J.T. Prog. Lipid Res. 1997; 36: 1-21Crossref PubMed Scopus (511) Google Scholar, 9Montine T.J. Markesbery W.R. Zackert W.E. Sanchez S.C. Roberts II, L.J. Morrow J.D. Am. J. Pathol. 1999; 155: 863-868Abstract Full Text Full Text PDF PubMed Scopus (100) Google Scholar). We have reported previously (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar, 10Roberts II, L.J. Montine T.J. Markesbery W.R. Tapper A.R. Hardy P. Chemtob S. Dettbarn W.D. Morrow J.D. J. Biol. Chem. 1998; 273: 13605-13612Abstract Full Text Full Text PDF PubMed Scopus (373) Google Scholar) that DHA is readily oxidized to generate 22-carbon isoprostane (IsoP)-like compounds, termed neuroprostanes (NPs). The formation of NPs from DHA is similar to the formation of IsoPs from arachidonic acid and proceeds via the generation of highly unstable endoperoxide intermediates (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar, 10Roberts II, L.J. Montine T.J. Markesbery W.R. Tapper A.R. Hardy P. Chemtob S. Dettbarn W.D. Morrow J.D. J. Biol. Chem. 1998; 273: 13605-13612Abstract Full Text Full Text PDF PubMed Scopus (373) Google Scholar). These intermediates can undergo reduction in vitro and in vivo to form NPs containing F-type prostane rings (F4-NPs) or can isomerize to molecules with E-type and D-type prostane rings (E4/D4-NPs). Levels of these compounds are significantly increased in the temporal and parietal cortices obtained from patients with Alzheimer's disease compared with control subjects (11Reich E.E. Markesbery W.R. Roberts II, L.J. Swift L.L. Morrow J.D. Montine T.J. Am. J. Pathol. 2001; 158: 293-297Abstract Full Text Full Text PDF PubMed Scopus (153) Google Scholar). DHA is concentrated in neurons, and we have thus suggested that NP formation may be a useful marker of selective neuronal oxidative injury. It is well known that eicosanoids containing E-type and D-type prostane rings are unstable and readily dehydrate in aqueous solutions to cyclopentenone-containing compounds (12Fitzpatrick F.A. Wynalda M.A. J. Biol. Chem. 1983; 258: 11713-11718Abstract Full Text PDF PubMed Google Scholar). For example PGE2and PGD2 can dehydrate to PGA2 and PGJ2, respectively. PGJ2 can undergo further metabolism to Δ12-PGJ2 and 15-deoxy-Δ12,14-PGJ2. Cyclopentenone PGs have attracted considerable interest because of their ability to modulate cell proliferation and differentiation. For example, various compounds of the A- and J-series have been shown to inhibit proliferation with a G1 cell cycle arrest and to induce differentiation (13Narumiya S. Ohno K. Fujiwara M. Fukushima M. J. Pharmacol. Exp. Ther. 1986; 239: 506-511PubMed Google Scholar, 14Cuzzocrea S. 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Roberts L.J. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). The biological of this to the fact that contain and are thus highly reactive and readily via Michael and protein Indeed, we have shown that in the of and the Y. Morrow J.D. Roberts L.J. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). The of and IsoPs may be for of the of oxidant in vivo. to the formation of from the dehydration of it would be that can undergo dehydration in the generation of cyclopentenone termed The of formation of from DHA is shown in DHA are and the addition of the undergo addition of to form endoperoxide These undergo to generate and is of for a total of and These molecules subsequently undergo dehydration to and of the total number of to The has and a system for the in the classes are the number of the the is with the as Morrow J.D. Roberts II, L.J. 1997; PubMed Scopus Google Scholar). this system to and can be as the the is with the obtained with NPs (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar). we that in formed in significant amounts in vitro and in vivo from the peroxidation of Docosahexaenoic and from and from hydrochloride from from from from and from from and from from and DHA oxidized in vitro an as previously Swift L.L. Roberts II, L.J. J.A. Morrow J.D. Pharmacol. 47: PubMed Scopus Google Scholar). obtained from oxidation of DHA or from other in and subsequently to incubation with in for at NPs as (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar, Y. Morrow J.D. Roberts L.J. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). The to a system of as previously for Y. Morrow J.D. Roberts L.J. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). in the from to the of PGA2 = with to trimethylsilyl ether and gas chromatography ion chemical ionization spectrometry The for of The in the mass of the ether of and the are the at and respectively. of of a or a of PGA2 with and has been shown to it to a ether is for Y. Morrow J.D. Roberts L.J. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). Thus, we for the formation of this of of putative with a of for at and the at for the NPs for compounds to to ether as J.D. Roberts L.J. 1990; PubMed Scopus Google Scholar). in of DHA a 25 with an system of acid at a of in for that amounts of with with of and in a of in the negative ion a The system a of acid to acid the of at a of The gas and the gas The the the and the from to dissociation of of putative in these from to from to The shown obtained at 25 The gas with a at a tissue obtained from rats and and J.T. J. 1986; 47: PubMed Scopus Google Scholar). Lipid peroxidation the addition of of at for The the at and the of E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar). in chemical with J.D. Roberts II, L.J. J.A. Swift L.L. 1998; PubMed Scopus Google Scholar), with in for at as for and levels of are to protein as the (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar). obtained from rats and parietal tissue in containing and to of to the they and and the aqueous The and in of and containing from other as with of of to the and with of and in this the with of to oxidized and of oxidized and of in the of to that for the rat as obtained from the in vitro oxidation of DHA and and in in the of a excess of and of containing a of at for Y. Morrow J.D. Roberts L.J. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). The incubation to and with of in the and NPs the the of to the that in the from a incubation definitively identified a with and Y. Morrow J.D. Roberts L.J. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar) and with of and a system in the with the of acid and compounds an at a of a mass in the ion electrospray with a and for and at and respectively. The at the at and and the For tandem compounds at an of and of and an ion obtained from the oxidation of DHA in vitro with for is shown in The large shown in the the and of the the ion are a of a These compounds a mass predicted for it would be predicted that the of be than that of the PGA2 because the compounds contain (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar). for PGA2 and PGJ2, as well as for the that have similar and and it is to A-type and J-type prostane rings in the putative NP compounds detected in ion shown in because and PGD2 readily dehydrate in aqueous solutions to form PGA2 and PGJ2, it is that the and would dehydrate to form and approaches to further that the compounds the in the ion the ion that the in the are of compounds an ion of than of putative as ether resulted in a of the to the of these compounds the to the of with resulted in the formation of ether The of as this to be ± ng/mg DHA ± = is than the formed compounds are as ether can be the fact that we have of PGA2 with it to a ether amounts of this are formed with a of the of would be to form a ether putative as ether to the in the intense at with the of at the of It be that it to putative ether because of the of these that the compounds the in ion shown in the and the number of predicted for that the compounds ion in the negative ion The and containing significant amounts of putative as a very from to this system The predicted to as for the ion of the ion at obtained from of the of putative cyclopentenone NPs from the at this from the as a of collision-induced dissociation obtained the in is shown in C. of the ion at resulted in the formation of a number of that would be predicted to be to of the including and are that may from of Because of the of and the of A- and it is to with the chemical of these the of (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar) and studies PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar), C. 1998; PubMed Scopus Google Scholar), and and Morrow J.D. Roberts II, L.J. Free Radic. Biol. Med. 1997; 23: PubMed Scopus (113) Google Scholar, J.A. E. M. J. Am. 1990; PubMed Scopus Google Scholar), of and other fatty acids these can be as and = = and = = and = = These suggested that the mass shown in a of that would be predicted to be of other similar mass the of significantly that various from the in It is of interest to that of the that are shown in from the of are we have reported previously (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. 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Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar) that levels of and NPs are in that are at an order of magnitude than the that the formation of A/J-ring NPs is other classes of these that of may be a of lipid peroxidation in biological of central nervous system oxidative We to whether are in brain in vivo in and as compounds chemical of compounds in brain lipid from ion obtained from of these is shown in The in the ion of the in this the is significantly than the and the the are a of that have and for The of A- and NPs very similar to that obtained from the oxidation of DHA in for in to studies in to further that the in the ion in formed in vivo. The compounds as ether resulted in a of the in ion of the of of the compounds as resulted in the of the to the of with resulted in the formation of a of with of the that these compounds can form ether these that the compounds in the in have the number of that are predicted for Levels of in the of rat brain to be 97 ± 25 ng/g (n = These amounts are significantly higher nearly an order of magnitude than reported for or We also amounts of in rat brain and they of levels of in parietal from humans obtained at known disease at the of a ion from a brain the of the are in the the are a of that have and for The of compounds is very similar to that obtained from the incubation of Levels of putative to be 98 ± 26 ng/g of brain tissue (n = with rat brain quantities of A/J-ring NPs of and NPs at the that formation of cyclopentenone NPs in the central nervous system is of in whether cyclopentenone NPs are formed in vivo is to the fact that be highly reactive because they contain and would thus be to addition Y. Morrow J.D. Roberts L.J. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). Thus, we to whether obtained from the oxidation of vitro would in the of We have shown previously Y. Morrow J.D. Roberts L.J. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar) that cyclopentenone eicosanoids including the isoprostane adduct in the of Because of the of we whether significant of these compounds with a the of is in of of cyclopentenone NPs the of NPs that at We that ± of the in in the form of a that would (n = similar of formed a with Y. Morrow J.D. Roberts L.J. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). These that cyclopentenone are reactive molecules of putative definitively identified from an incubation and to as The ion for ion of from the showed from to of obtained these and is shown in is the ion is of the and that of of These studies the of a of cyclopentenone vivo from the radical-initiated peroxidation of DHA is a unsaturated fatty acid in neural to neuronal as has been implicated in a number of neurodegenerative (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar, B. Gutteridge J.M.C. Methods Enzymol. 1990; 186: 1-85Crossref PubMed Scopus (4428) Google Scholar, 6Markesbery W.R. Free Radic. Biol. Med. 1997; 23: 134-147Crossref PubMed Scopus (1966) Google Scholar, 7Knight J.A. Ann. Clin. Lab. Sci. 1997; 27: 11-25PubMed Google Scholar, 8Simonian N.A. Doyle J.T. Prog. Lipid Res. 1997; 36: 1-21Crossref PubMed Scopus (511) Google Scholar, 9Montine T.J. Markesbery W.R. Zackert W.E. Sanchez S.C. Roberts II, L.J. Morrow J.D. Am. J. Pathol. 1999; 155: 863-868Abstract Full Text Full Text PDF PubMed Scopus (100) Google Scholar). the at a of that are formed from the oxidation of DHA has been the for the studies reported The of formation of from DHA is in We have reported previously (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar, 10Roberts II, L.J. Montine T.J. Markesbery W.R. Tapper A.R. Hardy P. Chemtob S. Dettbarn W.D. Morrow J.D. J. Biol. Chem. 1998; 273: 13605-13612Abstract Full Text Full Text PDF PubMed Scopus (373) Google Scholar) that and NPs are formed the with from of endoperoxide are reduction of the are formed dehydration of It be from the studies that in biological to in vitro and in cyclopentenone NPs are formed in significantly amounts than or These that the formation of cyclopentenone NPs is a of DHA oxidative these the that of may be a of DHA oxidation and neural tissue oxidative than other classes of that may the formation of A/J-ring NPs other NPs are we have shown previously J.D. Roberts II, L.J. J.A. Swift L.L. 1998; PubMed Scopus Google Scholar) that as and other endoperoxide intermediates in generation of It thus be predicted that the of would cyclopentenone this has been The studies also that the dehydration of to A/J-ring NPs because we detected significant amounts of the compounds DHA oxidized in the other it be that the dehydration of in vivo to other classes of the are formed in in and are in the form a (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar). We have previously that are for The of that be for of NPs from in is it has been reported previously E. Free Radic. Biol. Med. Scopus Google Scholar) that the of is oxidized the and the formation and of is of considerable because they would be predicted to be very molecules and thus of neuronal in of oxidant formation of neuronal and The of the formation of cyclopentenone NPs in for The reactive of these compounds the that them a for their in the pathogenesis of oxidant injury. Cyclopentenone PGs have been shown to biological inhibit proliferation via their ability to modulate a of and induce cell at higher and the Sci. S. 1997; PubMed Scopus Google Scholar, M. 1990; Google Scholar, M. M. L.L. Sci. S. 2000; PubMed Scopus Google Scholar, 1998; PubMed Scopus Google Scholar, 1993; PubMed Scopus Google Scholar, P. Chen J. Full Text PDF PubMed Scopus Google Scholar, I. Full Text PDF PubMed Scopus Google Scholar, C.J. 1998; PubMed Scopus Google Scholar, 1997; 5: Full Text PDF PubMed Scopus Google Scholar). The reactive for of the biological this that of these biological also be cyclopentenone in as the central nervous system they are formed in significant cyclopentenone NPs undergo glutathione with to PGA2 and Y. Morrow J.D. Roberts L.J. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). may also to and tissue injury in of oxidative of It has been shown that of cyclopentenone PGs with the biological of these reactive compounds L.J. Res. PubMed Scopus Google Scholar). Thus, to be known the that the biological of cyclopentenone these vitro and in vivo a of chemical and approaches of the of eicosanoids compared with are with studies and other (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar, PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar, C. 1998; PubMed Scopus Google Scholar, Morrow J.D. Roberts II, L.J. Free Radic. Biol. Med. 1997; 23: PubMed Scopus (113) Google Scholar, J.A. E. M. J. Am. 1990; PubMed Scopus Google Scholar). is a mass a number of the of of and are readily other can be that are derived from are the abundant and These are with at in the of 98 from the ion of and The ion has an of (3Reich E.E. Zackert W.E. Brame C.J. Chen Y. Roberts II, L.J. Hachey D.L. Montine T.J. Morrow J.D. Biochemistry. 2000; 39: 2376-2383Crossref PubMed Scopus (68) Google Scholar, PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar, C. 1998; PubMed Scopus Google Scholar, Morrow J.D. Roberts II, L.J. Free Radic. Biol. Med. 1997; 23: PubMed Scopus (113) Google Scholar, J.A. E. M. J. Am. 1990; PubMed Scopus Google Scholar) have a similar of 98 for various fatty and NPs ion that can be in the mass shown in ion can be at in as an from the of from the have been reported previously for and fatty we the that A/J-ring NPs are vivo as a of the peroxidation of a unsaturated fatty acid in neural The fact that are readily in brain from and humans at significantly higher than other classes of NPs the compounds an important of the oxidative metabolism of these the that is significant oxidant in the central nervous system. of the biological of the formation of these compounds and their formation and metabolism the of oxidant injury in the nervous system.