Formation of Highly Reactive γ-Ketoaldehydes (Neuroketals) as Products of the Neuroprostane Pathway

Bernoud-Hubac, Nathalie; Davies, Sean S.; Boutaud, Olivier; Montine, Thomas J.; Roberts, L. Jackson

doi:10.1074/jbc.m103768200

Cited by 95 publications

(77 citation statements)

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“…Oxidation of PUFAs in lipoproteins is known to yield a complex array of products, both protein-bound and free in solution, including isoprostane-derived levuglandin (27,28) and isoketal (29,30) derivatives and numerous keto and hydroxy fatty acids (11). A range of smaller, more polar aldehydes, ketoaldehydes, alkenals, and hydroxyalkenals are also released into solution and react with protein to form Schiff bases, Michael adducts, and pyrrole and pyridinium compounds that contribute to the brown color, fluorescence, and cross-linking of oxidized lipoproteins.…”

Section: Discussionmentioning

confidence: 99%

Chemical modification of proteins during peroxidation of phospholipids

Januszewski

Alderson

Jenkins

et al. 2005

Journal of Lipid Research

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Chemical modification of proteins by advanced glycation and lipoxidation end products is implicated in the pathogenesis of macrovascular disease in aging and diabetes. To identify biomarkers of the lipoxidative modification of protein, we studied the oxidation of phospholipids in the presence of the model protein RNase A and compared protein-bound products formed in these reactions with those formed during oxidation of plasma proteins. Metal-catalyzed oxidation of 1-palmitoyl-2-arachidonoyl-phosphatidylcholine or 1-palmitoyl-2-linoleoyl-phosphatidylcholine in the presence of RNase led to the loss of amino groups in RNase and the incorporation of phosphate, hexanoate, pentanedioate, nonanedioate, and palmitate into protein. Protein-bound palmitate and phosphate correlated strongly with one another, and protein-bound pentanedioate and nonanedioate, derived from arachidonate and linoleate, respectively, accounted for ‫ف‬ 20% of the cross-linking of lipid phosphorus to protein. Similar results were obtained on oxidation of total plasma or isolated LDL. We conclude that alkanedioic acids are quantitatively important linkers of oxidized phospholipids to proteins and that measurement of proteinbound phosphate and long-chain fatty acids may be useful for assessing long-term lipid peroxidative damage to proteins in vivo. Analyses of plasma proteins from control and diabetic patients indicated significant increases in lipoxidative modification of protein in diabetic compared with control subjects. -Januszewski, A.

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Section: Discussionmentioning

confidence: 99%

Chemical modification of proteins during peroxidation of phospholipids

Januszewski

Alderson

Jenkins

et al. 2005

Journal of Lipid Research

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“…After incubation, platelets were pelleted at 2,000 × g for 10 min at 4 °C. After centrifugation, the lysyl-levuglandin-lactam adduct was isolated from a proteolytic digest of the pelleted proteins and analyzed by high-performance liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS) as described previously (1,10,44). Levels of prostaglandin E 2 (PGE 2 ) in the platelet supernatant were analyzed by GC/MS as previously described (2).…”

Section: Measurement Of Cyclooxygenase Products In Plateletsmentioning

confidence: 99%

Pyridoxamine Analogues Scavenge Lipid-Derived γ-Ketoaldehydes and Protect against H₂O₂-Mediated Cytotoxicity

et al. 2006

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Isoketals and levuglandins are highly reactive γ-ketoaldehydes formed by oxygenation of arachidonic acid in settings of oxidative injury and cyclooxygenase activation, respectively. These compounds rapidly adduct to proteins via lysyl residues, which can alter protein structure/function. We examined whether pyridoxamine, which has been shown to scavenge α-ketoaldehydes formed by carbohydrate or lipid peroxidation, could also effectively protect proteins from the more reactive γ-ketoaldehydes. Pyridoxamine prevented adduction of ovalbumin and also prevented inhibition of RNase A and glutathione reductase activity by the synthetic γ-ketoaldehyde, 15-E 2 -isoketal. We identified the major products of the reaction of pyridoxamine with the 15-E 2 -isoketal, including a stable lactam adduct. Two lipophilic analogs of pyridoxamine, salicylamine and 5'O-pentylpyridoxamine, also formed lactam adducts when reacted with 15-E 2 -isoketal. When we oxidized arachidonic acid in the presence of pyridoxamine or its analogs, pyridoxamine-isoketal adducts were found in significantly greater abundance than the pyridoxamine-N-acyl adducts formed by α-ketoaldehyde scavenging. Therefore, pyridoxamine and its analogs appear to preferentially scavenge γ-ketoaldehydes. Both pyridoxamine and its lipophilic analogs inhibited the formation of lysyl-levuglandin adducts in platelets activated ex vivo with arachidonic acid. The two lipophilic pyridoxamine analogs provided significant protection against H 2 O 2 -mediated cytotoxicity in HepG2 cells. These results demonstrate the utility of pyridoxamine and lipophilic pyridoxamine analogs to assess the potential contributions of isoketals and levuglandins in oxidant injury and inflammation and suggest their potential utility as pharmaceutical agents in these conditions.Highly reactive γ-ketoaldehydes are formed via the cyclooxygenase pathway and by radicalcatalyzed lipid peroxidation. Prostaglandin H 2 , the product of the cyclooxygenase enzyme, rearranges in aqueous solution to form a number of eicosanoids, approximately 20% of which are the γ-ketoaldehydes levuglandin E 2 and D 2 . Lipid peroxidation yields a series of † This work was supported by National Institutes of Health Grants GM42056 (MERIT Award to L.J.R.), AG26119, GM15431 (to J . NIH Public Access Author ManuscriptBiochemistry. Author manuscript; available in PMC 2008 December 8. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript prostaglandin H 2 isomers that also rearrange to corresponding γ-ketoaldehydes, designated as isoketals (IsoK). These γ-ketoaldehydes (γKAs) react extremely rapidly with the lysyl residues of protein to form stable adducts, including a lysyl-lactam adduct and intermolecular crosslinks (1-4). Levels of γKA adducts significantly increase in pathological conditions including atherosclerosis, end-stage renal disease, and Alzheimer's Disease (5,6). Increased γKA adduct formation has also been characterized in experimental models of oxidative injury and inflammation, including carb...

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“…1A). Analogous molecules, termed neuroketals, are formed from the free radical-catalyzed oxidation of docosahexanoic acid and form protein adducts analogous to those described below for IsoKs (9).…”

mentioning

confidence: 99%

Modification of Proteins by Isoketal-containing Oxidized Phospholipids

Brame¹,

Boutaud

Davies

et al. 2004

Journal of Biological Chemistry

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Oxidative stress frequently leads to altered function of membrane proteins. Isoketals are highly reactive products of the isoprostane pathway of free radical-induced lipid peroxidation that rapidly form covalent protein adducts and exhibit a remarkable proclivity to form protein cross links in vitro. Examination of isoketal adducts from an animal model of oxidative injury revealed that initial adducts were formed by isoketals esterified in phospholipids, representing a novel oxidative injuryassociated modification of proteins by phospholipids. Maturation of adducts involved cleavage from phospholipids and conversion of adducts to a more stable chemical form that can be detected for extended periods. Because initial adducts were formed by phospholipidesterified isoketals, the functional consequence of isoketal adduction was examined using a model membrane protein (a cardiac K ؉ channel). These studies revealed that isoketal adduction profoundly altered protein function, inhibiting potassium current in a dosedependent manner. These findings indicate that phospholipid-esterified isoketals rapidly adduct membrane proteins and that such modification can alter protein function, suggesting a generalized cellular mechanism for alteration of membrane function as a consequence of oxidative stress.Oxidative stress from the generation of free radicals has been implicated in the pathogenesis of a wide variety of human diseases including atherosclerosis, cancer, and neurodegenerative diseases (1-3). Fatty acids esterified in membrane phospholipids are a major target of attack by free radicals (4 -6). We have described previously the formation of a series of highly electrophilic ␥-ketoaldehyde isomers in vitro, which we term isoketals (IsoKs) 1 (7), by rearrangement of endoperoxide intermediates in the isoprostane pathway of free radical-induced peroxidation of phospholipid-esterified arachidonic acid (8). Incorporation of oxygen at different sites of arachidonyl radical formation results in the formation of 8 structural isomers, each of which is composed of 4 racemic diastereoisomers (see Fig. 1A). Analogous molecules, termed neuroketals, are formed from the free radical-catalyzed oxidation of docosahexanoic acid and form protein adducts analogous to those described below for IsoKs (9).IsoKs adduct covalently with the ⑀-amino group of lysine residues in vitro within seconds, which is orders of magnitude faster than has been reported for other products of lipid peroxidation, including 4-hydroxynonenal (7). This remarkable reactivity has precluded the detection of free IsoKs in vivo because of their sequestration as adducts. Therefore, we elucidated the nature of IsoK protein adducts in vitro as an initial step toward identifying the formation of IsoK adducts in vivo (7, 10). IsoKs initially form reversible Schiff base adducts which irreversibly cyclize to pyrroles. The pyrroles then undergo facile autoxidation to stable lactam and hydroxylactam adducts (see Fig. 1B) (7, 10). Consistent with this process, Schiff base adducts f...

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Formation of Highly Reactive γ-Ketoaldehydes (Neuroketals) as Products of the Neuroprostane Pathway

Cited by 95 publications

References 50 publications

Chemical modification of proteins during peroxidation of phospholipids

Chemical modification of proteins during peroxidation of phospholipids

Pyridoxamine Analogues Scavenge Lipid-Derived γ-Ketoaldehydes and Protect against H₂O₂-Mediated Cytotoxicity

Modification of Proteins by Isoketal-containing Oxidized Phospholipids

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Formation of Highly Reactive γ-Ketoaldehydes (Neuroketals) as Products of the Neuroprostane Pathway

Cited by 95 publications

References 50 publications

Chemical modification of proteins during peroxidation of phospholipids

Chemical modification of proteins during peroxidation of phospholipids

Pyridoxamine Analogues Scavenge Lipid-Derived γ-Ketoaldehydes and Protect against H2O2-Mediated Cytotoxicity

Modification of Proteins by Isoketal-containing Oxidized Phospholipids

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Pyridoxamine Analogues Scavenge Lipid-Derived γ-Ketoaldehydes and Protect against H₂O₂-Mediated Cytotoxicity