Publications by authors named "Irene Zagol-Ikapitte"

20 Publications

  • Page 1 of 1

Dicarbonyl Electrophiles Mediate Inflammation-Induced Gastrointestinal Carcinogenesis.

Gastroenterology 2020 Nov 13. Epub 2020 Nov 13.

Division of Gastroenterology, Hepatology, and Nutrition, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee; Center for Mucosal Inflammation and Cancer, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee; Veterans Affairs Tennessee Valley Healthcare System, Nashville, Tennessee.

Background & Aims: Inflammation in the gastrointestinal tract may lead to the development of cancer. Dicarbonyl electrophiles, such as isolevuglandins (isoLGs), are generated from lipid peroxidation during the inflammatory response and form covalent adducts with amine-containing macromolecules. Thus, we sought to determine the role of dicarbonyl electrophiles in inflammation-associated carcinogenesis.

Methods: The formation of isoLG adducts was analyzed in the gastric tissues of patients infected with Helicobacter pylori from gastritis to precancerous intestinal metaplasia, in human gastric organoids, and in patients with colitis and colitis-associated carcinoma (CAC). The effect on cancer development of a potent scavenger of dicarbonyl electrophiles, 5-ethyl-2-hydroxybenzylamine (EtHOBA), was determined in transgenic FVB/N insulin-gastrin (INS-GAS) mice and Mongolian gerbils as models of H pylori-induced carcinogenesis and in C57BL/6 mice treated with azoxymethane-dextran sulfate sodium as a model of CAC. The effect of EtHOBA on mutations in gastric epithelial cells of H pylori-infected INS-GAS mice was assessed by whole-exome sequencing.

Results: We show increased isoLG adducts in gastric epithelial cell nuclei in patients with gastritis and intestinal metaplasia and in human gastric organoids infected with H pylori. EtHOBA inhibited gastric carcinoma in infected INS-GAS mice and gerbils and attenuated isoLG adducts, DNA damage, and somatic mutation frequency. Additionally, isoLG adducts were elevated in tissues from patients with colitis, colitis-associated dysplasia, and CAC as well as in dysplastic tumors of C57BL/6 mice treated with azoxymethane-dextran sulfate sodium. In this model, EtHOBA significantly reduced adduct formation, tumorigenesis, and dysplasia severity.

Conclusions: Dicarbonyl electrophiles represent a link between inflammation and somatic genomic alterations and are thus key targets for cancer chemoprevention.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1053/j.gastro.2020.11.006DOI Listing
November 2020

Mitochondrial Isolevuglandins Contribute to Vascular Oxidative Stress and Mitochondria-Targeted Scavenger of Isolevuglandins Reduces Mitochondrial Dysfunction and Hypertension.

Hypertension 2020 Dec 5;76(6):1980-1991. Epub 2020 Oct 5.

From the Vanderbilt University Medical Center, Nashville, TN (A.D., L.X., V.A., I.Z.-I., A.V., M.A., V.Y., R.R.N., O.B., M.G.L., F.T.B., S. Davies, L.J.R., D.G.H., S. Dikalov).

Hypertension remains a major health problem in Western Societies, and blood pressure is poorly controlled in a third of patients despite use of multiple drugs. Mitochondrial dysfunction contributes to hypertension, and mitochondria-targeted agents can potentially improve treatment of hypertension. We have proposed that mitochondrial oxidative stress produces reactive dicarbonyl lipid peroxidation products, isolevuglandins, and that scavenging of mitochondrial isolevuglandins improves vascular function and reduces hypertension. To test this hypothesis, we have studied the accumulation of mitochondrial isolevuglandins-protein adducts in patients with essential hypertension and Ang II (angiotensin II) model of hypertension using mass spectrometry and Western blot analysis. The therapeutic potential of targeting mitochondrial isolevuglandins was tested by the novel mitochondria-targeted isolevuglandin scavenger, mito2HOBA. Mitochondrial isolevuglandins in arterioles from hypertensive patients were 250% greater than in arterioles from normotensive subjects, and ex vivo mito2HOBA treatment of arterioles from hypertensive subjects increased deacetylation of a key mitochondrial antioxidant, SOD2 (superoxide dismutase 2). In human aortic endothelial cells stimulated with Ang II plus TNF (tumor necrosis factor)-α, mito2HOBA reduced mitochondrial superoxide and cardiolipin oxidation, a specific marker of mitochondrial oxidative stress. In Ang II-infused mice, mito2HOBA diminished mitochondrial isolevuglandins-protein adducts, raised Sirt3 (sirtuin 3) mitochondrial deacetylase activity, reduced vascular superoxide, increased endothelial nitric oxide, improved endothelium-dependent relaxation, and attenuated hypertension. Mito2HOBA preserved mitochondrial respiration, protected ATP production, and reduced mitochondrial permeability pore opening in Ang II-infused mice. These data support the role of mitochondrial isolevuglandins in endothelial dysfunction and hypertension. We conclude that scavenging of mitochondrial isolevuglandins may have therapeutic potential in treatment of vascular dysfunction and hypertension.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/HYPERTENSIONAHA.120.15236DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7666054PMC
December 2020

Scavenging of reactive dicarbonyls with 2-hydroxybenzylamine reduces atherosclerosis in hypercholesterolemic Ldlr mice.

Nat Commun 2020 08 14;11(1):4084. Epub 2020 Aug 14.

Department of Medicine, Division of Cardiovascular Medicine, Atherosclerosis Research Unit, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA.

Lipid peroxidation generates reactive dicarbonyls including isolevuglandins (IsoLGs) and malondialdehyde (MDA) that covalently modify proteins. Humans with familial hypercholesterolemia (FH) have increased lipoprotein dicarbonyl adducts and dysfunctional HDL. We investigate the impact of the dicarbonyl scavenger, 2-hydroxybenzylamine (2-HOBA) on HDL function and atherosclerosis in Ldlr mice, a model of FH. Compared to hypercholesterolemic Ldlr mice treated with vehicle or 4-HOBA, a nonreactive analogue, 2-HOBA decreases atherosclerosis by 60% in en face aortas, without changing plasma cholesterol. Ldlr mice treated with 2-HOBA have reduced MDA-LDL and MDA-HDL levels, and their HDL display increased capacity to reduce macrophage cholesterol. Importantly, 2-HOBA reduces the MDA- and IsoLG-lysyl content in atherosclerotic aortas versus 4-HOBA. Furthermore, 2-HOBA reduces inflammation and plaque apoptotic cells and promotes efferocytosis and features of stable plaques. Dicarbonyl scavenging with 2-HOBA has multiple atheroprotective effects in a murine FH model, supporting its potential as a therapeutic approach for atherosclerotic cardiovascular disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-020-17915-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7429830PMC
August 2020

Highly Reactive Isolevuglandins Promote Atrial Fibrillation Caused by Hypertension.

JACC Basic Transl Sci 2020 Jun 27;5(6):602-615. Epub 2020 May 27.

Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee.

Oxidative damage is implicated in atrial fibrillation (AF), but antioxidants are ineffective therapeutically. The authors tested the hypothesis that highly reactive lipid dicarbonyl metabolites, or isolevuglandins (IsoLGs), are principal drivers of AF during hypertension. In a hypertensive murine model and stretched atriomyocytes, the dicarbonyl scavenger 2-hydroxybenzylamine (2-HOBA) prevented IsoLG adducts and preamyloid oligomers (PAOs), and AF susceptibility, whereas the ineffective analog 4-hydroxybenzylamine (4-HOBA) had minimal effect. Natriuretic peptides generated cytotoxic oligomers, a process accelerated by IsoLGs, contributing to atrial PAO formation. These findings support the concept of pre-emptively scavenging reactive downstream oxidative stress mediators as a potential therapeutic approach to prevent AF.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jacbts.2020.04.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7315188PMC
June 2020

Gastroesophageal Reflux Induces Protein Adducts in the Esophagus.

Cell Mol Gastroenterol Hepatol 2019 8;7(2):480-482.e7. Epub 2018 Nov 8.

Department of Surgery, University of Miami, Miami, Florida; Department of Surgery, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Veterans Affairs, Miami VA Healthcare System, Miami, Florida. Electronic address:

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jcmgh.2018.10.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6410348PMC
May 2019

Cyclooxygenase inhibition targets neurons to prevent early behavioural decline in Alzheimer's disease model mice.

Brain 2016 07 13;139(Pt 7):2063-81. Epub 2016 May 13.

1 Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA

Identifying preventive targets for Alzheimer's disease is a central challenge of modern medicine. Non-steroidal anti-inflammatory drugs, which inhibit the cyclooxygenase enzymes COX-1 and COX-2, reduce the risk of developing Alzheimer's disease in normal ageing populations. This preventive effect coincides with an extended preclinical phase that spans years to decades before onset of cognitive decline. In the brain, COX-2 is induced in neurons in response to excitatory synaptic activity and in glial cells in response to inflammation. To identify mechanisms underlying prevention of cognitive decline by anti-inflammatory drugs, we first identified an early object memory deficit in APPSwe-PS1ΔE9 mice that preceded previously identified spatial memory deficits in this model. We modelled prevention of this memory deficit with ibuprofen, and found that ibuprofen prevented memory impairment without producing any measurable changes in amyloid-β accumulation or glial inflammation. Instead, ibuprofen modulated hippocampal gene expression in pathways involved in neuronal plasticity and increased levels of norepinephrine and dopamine. The gene most highly downregulated by ibuprofen was neuronal tryptophan 2,3-dioxygenase (Tdo2), which encodes an enzyme that metabolizes tryptophan to kynurenine. TDO2 expression was increased by neuronal COX-2 activity, and overexpression of hippocampal TDO2 produced behavioural deficits. Moreover, pharmacological TDO2 inhibition prevented behavioural deficits in APPSwe-PS1ΔE9 mice. Taken together, these data demonstrate broad effects of cyclooxygenase inhibition on multiple neuronal pathways that counteract the neurotoxic effects of early accumulating amyloid-β oligomers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/brain/aww117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4939702PMC
July 2016

Protein modification by adenine propenal.

Chem Res Toxicol 2014 Oct 24;27(10):1732-42. Epub 2014 Sep 24.

A. B. Hancock Jr. Memorial Laboratory for Cancer Research, Departments of Biochemistry, ‡Chemistry, and §Pharmacology, ∥Mass Spectrometry Research Center, ⊥Center in Molecular Toxicology, #Center for Structural Biology, ∇Department of Medicine, Vanderbilt Institute of Chemical Biology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States.

Base propenals are products of the reaction of DNA with oxidants such as peroxynitrite and bleomycin. The most reactive base propenal, adenine propenal, is mutagenic in Escherichia coli and reacts with DNA to form covalent adducts; however, the reaction of adenine propenal with protein has not yet been investigated. A survey of the reaction of adenine propenal with amino acids revealed that lysine and cysteine form adducts, whereas histidine and arginine do not. N(ε)-Oxopropenyllysine, a lysine-lysine cross-link, and S-oxopropenyl cysteine are the major products. Comprehensive profiling of the reaction of adenine propenal with human serum albumin and the DNA repair protein, XPA, revealed that the only stable adduct is N(ε)-oxopropenyllysine. The most reactive sites for modification in human albumin are K190 and K351. Three sites of modification of XPA are in the DNA-binding domain, and two sites are subject to regulatory acetylation. Modification by adenine propenal dramatically reduces XPA's ability to bind to a DNA substrate.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/tx500218gDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4203390PMC
October 2014

Suppression of Alzheimer-associated inflammation by microglial prostaglandin-E2 EP4 receptor signaling.

J Neurosci 2014 Apr;34(17):5882-94

Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California 94305, Neurosciences Graduate Program, Stanford University, Stanford, California 94305, and Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232.

A persistent and nonresolving inflammatory response to accumulating Aβ peptide species is a cardinal feature in the development of Alzheimer's disease (AD). In response to accumulating Aβ peptide species, microglia, the innate immune cells of the brain, generate a toxic inflammatory response that accelerates synaptic and neuronal injury. Many proinflammatory signaling pathways are linked to progression of neurodegeneration. However, endogenous anti-inflammatory pathways capable of suppressing Aβ-induced inflammation represent a relatively unexplored area. Here we report that signaling through the prostaglandin-E2 (PGE2) EP4 receptor potently suppresses microglial inflammatory responses to Aβ42 peptides. In cultured microglial cells, EP4 stimulation attenuated levels of Aβ42-induced inflammatory factors and potentiated phagocytosis of Aβ42. Microarray analysis demonstrated that EP4 stimulation broadly opposed Aβ42-driven gene expression changes in microglia, with enrichment for targets of IRF1, IRF7, and NF-κB transcription factors. In vivo, conditional deletion of microglial EP4 in APPSwe-PS1ΔE9 (APP-PS1) mice conversely increased inflammatory gene expression, oxidative protein modification, and Aβ deposition in brain at early stages of pathology, but not at later stages, suggesting an early anti-inflammatory function of microglial EP4 signaling in the APP-PS1 model. Finally, EP4 receptor levels decreased significantly in human cortex with progression from normal to AD states, suggesting that early loss of this beneficial signaling system in preclinical AD development may contribute to subsequent progression of pathology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1523/JNEUROSCI.0410-14.2014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3996215PMC
April 2014

Levuglandin forms adducts with histone h4 in a cyclooxygenase-2-dependent manner, altering its interaction with DNA.

Biochemistry 2014 Apr 11;53(15):2436-41. Epub 2014 Apr 11.

Departments of †Pharmacology, ‡Pathology, and §Medicine, Vanderbilt University , Nashville, Tennessee 37232, United States.

Inflammation and subsequent cyclooxygenase-2 (COX-2) activity has long been linked with the development of cancer, although little is known about any epigenetic effects of COX-2. A product of COX-2 activation, levuglandin (LG) quickly forms covalent bonds with nearby primary amines, such as those in lysine, which leads to LG-protein adducts. Here, we demonstrate that COX-2 activity causes LG-histone adducts in cultured cells and liver tissue, detectable through LC-MS, with the highest incidence in histone H4. Adduction is blocked by a γ-ketoaldehyde scavenger, which has no effect on COX-2 activity as measured by PGE2 production. Formation of the LG-histone adduct is associated with an increased histone solubility in NaCl, indicating destabilization of the nucleosome structure; this is also reversed with scavenger treatment. These data demonstrate that COX-2 activity can cause histone adduction and loosening of the nucleosome complex, which could lead to altered transcription and contribute to carcinogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/bi401673bDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4004227PMC
April 2014

Rational Design of Novel Pyridinol-Fused Ring Acetaminophen Analogues.

ACS Med Chem Lett 2013 Aug;4(8):710-714

Department of Pharmacology, Division of Clinical Pharmacology, Vanderbilt University Medical Center, 536 Robinson Research Building, Nashville, Tennessee 37232-6602, United States.

Acetaminophen (ApAP) is an electron donor capable of reducing radicals generated by redox cycling of hemeproteins. It acts on the prostaglandin H synthases (cyclooxygenases; COXs) to reduce the protoporphyrin radical cation in the peroxidase site of the enzyme, thus preventing the intra-molecular electron transfer that generates the Tyr385 radical required for abstraction of a hydrogen from arachidonic acid to initiate prostaglandin synthesis. Unrelated to this pharmacological action, metabolism of ApAP by CYPs yields an iminoquinone electrophile that is responsible for the hepatotoxicity, which results from high doses of the drug. We synthesized novel heterocyclic phenols predicted to be electron donors. Two of these inhibited the oxygenation of arachidonic acid by PGHS-1 and myoglobin and also were shown to be more metabolically stable and exhibited less direct cytotoxicity than acetaminophen. They are leading candidates for studies to determine whether they are free of the metabolism-based hepatotoxicity produced by acetaminophen.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ml4000904DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3904457PMC
August 2013

On-tissue chemical derivatization of 3-methoxysalicylamine for MALDI-imaging mass spectrometry.

J Mass Spectrom 2011 Aug;46(8):840-6

Department of Pharmacology, Vanderbilt University, Nashville, TN 37232-6602, USA.

MALDI-imaging mass spectrometry (IMS) has been shown to be a powerful tool to study drug distributions in organ tissue as well as whole animal bodies. Nevertheless, not all drugs are amenable to MALDI while others may be limited by poor sensitivity poor sensitivity. The use of chemical derivatization to improve detection of small molecules by mass spectrometry techniques is well documented. To our knowledge, however, this approach has not been applied to direct tissue analysis of small organic molecules. In this manuscript, we demonstrate the use of on-tissue chemical derivatization of a small organic molecule, 3-methoxysalicylamine (3-MoSA) a scavenger of γ-ketoaldehydes. Derivatization of 3-MoSA with 1,1'-thiocarbonyldiimidazole (TCDI) results in an oxothiazolidine derivative which is detected with much greater sensitivity by MALDI than 3-MoSA itself. TCDI treatment of tissue from mice dosed with 3-MoSA allowed images to be obtained showing its spatial distribution as well as its pharmacokinetic profile in different organs. These images correlated well with results obtained from HPLC-MS/MS analyses of the same tissues. These results provide proof-of-concept that on-tissue chemical derivatization can be used to improve detection of a small organic molecule by MALDI-IMS.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jms.1958DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3174490PMC
August 2011

Determination of 3-methoxysalicylamine levels in mouse plasma and tissue by liquid chromatography-tandem mass spectrometry: application to in vivo pharmacokinetics studies.

J Chromatogr B Analyt Technol Biomed Life Sci 2011 May 21;879(15-16):1098-104. Epub 2011 Mar 21.

Department of Pharmacology, Vanderbilt University, Nashville, TN 37232-6602, USA.

We report the development of a sensitive liquid chromatography-tandem mass spectrometric assay to quantitate 3-methoxysalicylamine (3-MoSA) in biological samples. Derivatization with 1,1'-thiocarbonyldiimidazole followed by C(18) reverse-phase chromatography allowed the detection of both analyte and internal standard (hexylsalicylamine) using electrospray ionization and selected reaction monitoring (SRM) in positive ion mode. We monitored the transitions from m/z 196.7 to 65.1 and from m/z 250.1 to 77.1 for 3-MoSA and HxSA, respectively. The method is validated with respect to linearity (r(2)=0.995), precision (<17% RSD), recovery (100% for 3-MoSA and HxSA), and stability (77% after storage up to 7 month at -80°C). The LOD and LOQ were 16.12 and 48.87 μg/l, respectively and the LLOQ of 1 pg/ml. In addition, we used this assay to analyze the pharmacokinetics of 3-MoSA in mouse plasma and tissues following both intraperitoneal and oral administration, providing new information regarding the distribution of this compound in vivo.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jchromb.2011.03.026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3091354PMC
May 2011

Determination of the Pharmacokinetics and Oral Bioavailability of Salicylamine, a Potent γ-Ketoaldehyde Scavenger, by LC/MS/MS.

Pharmaceutics 2010 Mar;2(1):18-29

Division of Clinical Pharmacology, Departments of Pharmacology, Medicine, and Pathology, Vanderbilt University, Nashville, TN, USA; (I.A.Z.-I.); (E.M.); (V.A.); (C.L.B.); (O.B.); (J.A.O.); (L.J.R.).

Levels of reactive γ-ketoaldehydes derived from arachidonate increase in diseases associated with inflammation and oxidative injury. To assess the biological importance of these γ-ketoaldehydes, we previously identified salicylamine as an effective γ-ketoaldehyde scavenger in vitro and in cells. To determine if salicylamine could be administered in vivo, we developed an LC/MS/MS assay to measure salicylamine in plasma and tissues. In mice, half-life (t(1/2)) was 62 minutes. Drinking water supplementation (1-10 g/L) generated tissue concentrations (10-500 μM) within the range previously shown to inhibit γ-ketoaldehydes in cells. Therefore, oral administration of salicylamine can be used to assess the contribution of γ-ketoaldehydes in animal models of disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/pharmaceutics2010018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3150493PMC
March 2010

Antioxidant supplementation had positive effects in old rat muscle, but through better oxidative status in other organs.

Nutrition 2010 Nov-Dec;26(11-12):1157-62. Epub 2010 Jan 15.

INRA, UMR 1019 Nutrition Humaine, Saint Genès Champanelle, France.

Objective: Aged muscle is characterized by a defect in the ability of leucine to stimulate protein synthesis. We showed previously that antioxidant supplementation improved the anabolic response to leucine of old muscle and reduced inflammation. The aim of the present study was to determine if the positive effects observed in muscle could be related to an improvement of local muscle oxidative status.

Methods: Two groups of 20-mo-old male Wistar rats were supplemented or not with rutin, vitamin E, vitamin A, zinc, and selenium during 7 wk. We measured body weight, food intake, oxidative status in muscle and other tissues, gastrocnemius muscle proteolytic activities, and liver glutathione metabolism.

Results: Antioxidant supplementation had no effect on muscle antioxidant capacity, superoxide dismutase activities, and myofibrillar protein carbonyl content and induced an increase in muscle cathepsin activities. In other tissues, antioxidant supplementation increased liver glutathione (reduced plus oxidized glutathione) content, reduced oxidative damage in the liver and spleen (as measured by γ-keto-aldehyde content), and reduced heart thiobarbituric acid-reactive substances.

Conclusion: Our results showed that the positive effects of antioxidant supplementation observed previously on the anabolic response to leucine of old muscle were not directly related to an improvement of in situ muscle oxidative status. It could result from reduced systemic inflammation/oxidative stress. The dialog between muscle and other organs should be studied more thoroughly, especially during aging.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.nut.2009.09.016DOI Listing
February 2011

Characterization of scavengers of gamma-ketoaldehydes that do not inhibit prostaglandin biosynthesis.

Chem Res Toxicol 2010 Jan;23(1):240-50

Departments of Pharmacology, Pathology, and Medicine, Vanderbilt University, Nashville, Tennessee 37232-6602, USA.

Expression of cyclooxygenase-2 (COX-2) is associated with the development of many pathologic conditions. The product of COX-2, prostaglandin H(2) (PGH(2)), can spontaneously rearrange to form reactive gamma-ketoaldehydes called levuglandins (LGs). This gamma-ketoaldehyde structure confers a high degree of reactivity on the LGs, which rapidly form covalent adducts with primary amines of protein residues. Formation of LG adducts of proteins has been demonstrated in pathologic conditions (e.g., increased levels in the hippocampus in Alzheimer's disease) and during physiologic function (platelet activation). On the basis of knowledge that lipid modification of proteins is known to cause their translocation and to alter their function, we hypothesize that modification of proteins by LG could have functional consequences. Testing this hypothesis requires an experimental approach that discriminates between the effects of protein modification by LG and the effects of cyclooxygenase-derived prostanoids acting through their G-protein coupled receptors. To achieve this goal, we have synthesized and evaluated a series of scavengers that react with LG with a potency more than 2 orders of magnitude greater than that with the epsilon-amine of lysine. A subset of these scavengers are shown to block the formation of LG adducts of proteins in cells without inhibiting the catalytic activity of the cyclooxygenases. Ten of these selective scavengers did not produce cytotoxicity. These results demonstrate that small molecules can scavenge LGs in cells without interfering with the formation of prostaglandins. They also provide a working hypothesis for the development of pharmacologic agents that could be used in experimental animals in vivo to assess the pathophysiological contribution of levuglandins in diseases associated with cyclooxygenase up-regulation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/tx900407aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2831641PMC
January 2010

Pyridine and pyrimidine analogs of acetaminophen as inhibitors of lipid peroxidation and cyclooxygenase and lipoxygenase catalysis.

Org Biomol Chem 2009 Dec 20;7(24):5103-12. Epub 2009 Oct 20.

Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA.

Herein we report an investigation of the efficacy of pyridine and pyrimidine analogs of acetaminophen (ApAP) as peroxyl radical-trapping antioxidants and inhibitors of enzyme-catalyzed lipid peroxidation by cyclooxygenases (COX) and lipoxygenases (LOX). In inhibited autoxidations we find that ApAP, the common analgesic and antipyretic agent, is a very good antioxidant with a rate constant for reaction with peroxyl radicals (k(inh) = 5 x 10(5) M(-1) s(-1)) that is higher than many widely-used phenolic antioxidants, such as the ubiquitous butylated hydroxytoluene (BHT). This reactivity is reduced substantially upon incorporation of nitrogen into the phenolic ring, owing to an increase in the O-H bond dissociation enthalpy of pyridinols and pyrimidinols with respect to phenols. Incorporation of nitrogen into the phenolic ring of ApAP was also found to decrease its efficacy as an inhibitor of prostaglandin biosynthesis by ovine COX-1 (oCOX-1). This is explained on the basis of an increase in its oxidation potential and its reduced reactivity as a reducing co-substrate of the peroxidase protoporphyrin. In contrast, the efficacy of ApAP as an inhibitor of lipid hydroperoxide biosynthesis by soybean LOX-1 (sLOX-1) increased upon incorporation of nitrogen into the ring, suggesting a different mechanism of inhibition dependent on the acidity of the phenolic O-H which may involve chelation of the catalytic non-heme iron atom. The greater stability of the 3-pyridinols and 5-pyrimidinols to air oxidation as compared to phenols allowed us to evaluate some electron-rich pyridinols and pyrimidinols as inhibitors of oCOX-1 and sLOX-1. While the pyridinols had the best combination of activities as antioxidants and inhibitors of oCOX-1 and sLOX-1, they were found to be more toxic than ApAP in preliminary assays in human hepatocellular carcinoma (HepG2) cell culture. The pyrimidinols, however, were up to 17-fold more reactive to peroxyl radicals and up to 25-fold better inhibitors of prostaglandin biosynthesis than ApAP, with similar cytotoxicities to HepG2 cells at high levels of exposure.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/b912528kDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2873786PMC
December 2009

Pyridoxamine analogues scavenge lipid-derived gamma-ketoaldehydes and protect against H2O2-mediated cytotoxicity.

Biochemistry 2006 Dec 6;45(51):15756-67. Epub 2006 Dec 6.

Departments of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232, USA.

Isoketals and levuglandins are highly reactive gamma-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 alpha-ketoaldehydes formed by carbohydrate or lipid peroxidation, could also effectively protect proteins from the more reactive gamma-ketoaldehydes. Pyridoxamine prevented adduction of ovalbumin and also prevented inhibition of RNase A and glutathione reductase activity by the synthetic gamma-ketoaldehyde, 15-E2-isoketal. We identified the major products of the reaction of pyridoxamine with the 15-E2-isoketal, including a stable lactam adduct. Two lipophilic analogues of pyridoxamine, salicylamine and 5'-O-pentylpyridoxamine, also formed lactam adducts when reacted with 15-E2-isoketal. When we oxidized arachidonic acid in the presence of pyridoxamine or its analogues, pyridoxamine-isoketal adducts were found in significantly greater abundance than the pyridoxamine-N-acyl adducts formed by alpha-ketoaldehyde scavenging. Therefore, pyridoxamine and its analogues appear to preferentially scavenge gamma-ketoaldehydes. Both pyridoxamine and its lipophilic analogues inhibited the formation of lysyl-levuglandin adducts in platelets activated ex vivo with arachidonic acid. The two lipophilic pyridoxamine analogues provided significant protection against H2O2-mediated cytotoxicity in HepG2 cells. These results demonstrate the utility of pyridoxamine and lipophilic pyridoxamine analogues 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/bi061860gDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2597444PMC
December 2006

Prostaglandin H(2)-derived adducts of proteins correlate with Alzheimer's disease severity.

J Neurochem 2005 Aug 30;94(4):1140-5. Epub 2005 Jun 30.

Department of Pharmacology, Vanderbilt University, Nashville, TN, USA.

The formation of cyclooxygenase-derived lipid adducts of protein in brains of patients who had Alzheimer's disease has been investigated. The enzymatic product of the cyclooxygenases, prostaglandin H2, rearranges in part to highly reactive gamma-ketoaldehydes, levuglandin (LG) E(2) and LGD(2). These gamma-ketoaldehydes react with free amines on proteins to yield a covalent adduct. Utilizing analysis of the levuglandinyl-lysine adducts by liquid chromatography-tandem mass spectrometry, we now find that this post-translational modification is increased significantly in the hippocampus in Alzheimer's disease. The magnitude of the increase correlates with the pathological evidence of severity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1471-4159.2005.03264.xDOI Listing
August 2005

Cyclooxygenase-dependent lipid-modification of brain proteins.

Brain Pathol 2005 Apr;15(2):139-42

Department of Pharmacology, Vanderbilt University, Nashville, TN 37232-6602, USA.

Substantial evidence indicates that both beta-amyloid and cyclooxygenase activity contribute to the pathogenesis of Alzheimer disease. The immediate product of the cyclooxygenases, prostaglandin H2, rapidly rearranges in aqueous solution, with approximately 20% being converted to levuglandins E2 and D2. These gamma-ketoaldehydes are highly reactive and rapidly adduct to accessible amine groups on macromolecules, particularly the epsilon-amine of lysine residues on proteins. The immediate LG-lysine adducts are themselves reactive, and can covalently crosslink proteins. PGH2, acting via LGs, accelerates the formation of the type of oligomers of amyloid beta that has been associated with neurotoxicity. In this review, we discuss the cyclooxygenase-dependent lipid-modification of proteins by levuglandins in vitro, in cells in culture and in vivo in transgenic mice over-expressing COX in the brain.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1750-3639.2005.tb00510.xDOI Listing
April 2005

Characterization of bis(levuglandinyl) urea derivatives as products of the reaction between prostaglandin H2 and arginine.

Biochemistry 2004 May;43(18):5503-10

Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232-6602, USA.

Levuglandins are gamma-keto aldehydes formed by rearrangement of prostaglandin (PG) H(2) in aqueous solution. Levuglandins are highly reactive with primary amines. We had previously characterized adducts formed after reaction of levuglandin E(2) (LGE(2)) or PGH(2) with lysine. In this study, we assessed whether reaction of PGH(2) with arginine yielded covalent adducts. Using N(alpha)-acetylarginine and both PGH(2) and synthetic LGE(2), we discovered a novel series of levuglandinyl adducts derived from reaction of two levuglandin moieties with the guanidino group of arginine. Subsequent spontaneous hydrolysis of the adducted amino acid yields bis(levuglandinyl) urea and the corresponding ornithine residue. Using liquid chromatography tandem mass spectrometry, we characterized the molecular structure of these novel adducts and demonstrated their formation after coincubation of PGH(2) with synthetic peptides and proteins. The soluble characteristic of these molecules provides a potential strategy for development of biological markers of lipid modification of proteins following cyclooxygenase activity or lipid peroxidation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/bi049842rDOI Listing
May 2004