Initiation Of Lipid Peroxidation Research Articles

Unraveling uranium induced oxidative stress related responses in Arabidopsis thaliana seedlings. Part II: responses in the leaves and general conclusions

The cellular redox balance seems an important modulator under heavy metal stress. While for other heavy metals these processes are well studied, oxidative stress related responses are also known to be triggered under uranium stress but information remains limited. This study aimed to further unravel the mechanisms by which plants respond to uranium stress. Seventeen-day-old Arabidopsis thaliana seedlings, grown on a modified Hoagland solution under controlled conditions, were exposed to 0, 0.1, 1, 10 and 100 μM uranium for 1, 3 and 7 days. While in Part I of this study oxidative stress related responses in the roots were discussed, this second Part II discusses oxidative stress related responses in the leaves and general conclusions drawn from the results of the roots and the leaves will be presented. As several responses were already visible following 1 day exposure, when uranium concentrations in the leaves were negligible, a root-to-shoot signaling system was suggested in which plastids could be important sensing sites. While lipid peroxidation, based on the amount of thiobarbituric acid reactive compounds, was observed after exposure to 100 μM uranium, affecting membrane structure and function, a transient concentration dependent response pattern was visible for lipoxygenase initiated lipid peroxidation. This transient character of uranium stress responses in leaves was emphasized by results of lipoxygenase (LOX2) and antioxidative enzyme transcript levels, enzyme capacities and glutathione concentrations both in time as with concentration. The ascorbate redox balance seemed an important modulator of uranium stress responses in the leaves as in addition to the previous transient responses, the total ascorbate concentration and ascorbate/dehydroascorbate redox balance increased in a concentration and time dependent manner. This could represent either a slow transient response or a stable increase with regard to plant acclimation to uranium stress.

Lipid Oxidation and Cardiovascular Disease: Introduction to a Review Series

A therosclerosis and the associated adverse complications of cardiovascular disease are major causes of morbidity and mortality in people living a Western lifestyle. A role for excess cholesterol in the pathophysiology of atherosclerosis is clear. However, additional mechanisms driving the relevant pathological changes in a chronic disease such as atherosclerosis are those that constitute the acute inflammatory response.1 The essential elements of a physiological, and regulated, inflammatory response starts with stimulated endothelium,2 displaying adhesive molecules for circulating white blood cells. This is accompanied by localized production of cell type–specific agonists for adherent monocytes, neutrophils, or lymphocytes by the activated endothelium.3 These agonists then activate the migratory instruction set of adherent or rolling cells positioned to receive both adhesion- and agonist-related stimuli from activated vascular endothelial cells.4 Lipid oxidation products formed by virtually every vascular cell type participate in orchestrating these processes. We also have recently come to appreciate that the inflammatory process is actively limited by activation of a resolution phase, often via generation of structurally specific oxidized lipids whose function is to orchestrate resolution of inflammation.5 The overall goal of this review series is to place recent observations and insights in rapidly developing areas of lipid oxidation into the framework of cardiovascular disease. Enzymatic and free radical oxidation have prominent roles in cardiovascular disease through their oxidative modification of existing molecules. Lipids are primary targets of this modification because they are the primary repository of oxidizable olefinic or double bonds. Oxidized lipids are best understood as oxygenated arachidonic acid products, the prostaglandins, leukotrienes, and thromboxane A2, that have diverse and potent effects throughout the inflammatory and reparative responses. These oxidized lipid mediators are …

Changes in Anti-Oxidant Enzyme Profile during Haematological Malignancy

Reactive oxygen species can initiate lipid peroxidation and DNA damage leading to mutagenesis, carcinogenesis and cell death, if the antioxidant system is impaired. The present work aimed to study the changes in the quantitative in vitro activities of the antioxidant enzymes - glutathione peroxidase and superoxide dismutase in the whole blood of our study group. Our study group included both blood cancer patients and age, sex matched healthy controls. We found significant decreases in the activities of both glutathione peroxidase and superoxide dismutase in patients as compared with healthy controls. Our previous work has indicated elevated arsenic concentration in the biosamples of patients. Thus, haematological malignancy is found to be associated with changes in the antioxidant defense system which is correlated with arsenic toxicity.

Composition and Biological Properties of the Volatile Oil of Artemisia gorgonumWebb

The chemical composition of Artemisia gorgonum Webb essential oil from Cape Verde was analyzed by GC and GC/MS. A total of 111 volatile compounds, accounting for 94.9% of the essential oil, were identified by GC and GC/MS. The major compounds were camphor (28.7%), chrysanthenone (10.8%), lavandulyl 2-methylbutanoate (9.5%), alpha-phellandrene (5.5%), lavandulyl propanoate (4.2%), camphene (4.0%), and p-cymene (3.4%). The volatile oil of this endemic plant, which is used in Cape Verdean folk medicine against several ailments, was tested for its antioxidant and antimalarial properties, and was found to exhibit free-radical scavenging on 1,1-diphenyl-2-picrylhydrazyl (DPPH), prevention of lipid peroxidation-in vitro by TBARS (thiobarbituric acid reactive species) assay, and antiplasmodial activity.

Antioxidants in Treating Pathologies Involving Oxidative Damage: An Update on Medicinal Chemistry and Biological Activity of Stobadine and Related Pyridoindoles

Pathologies involving oxidative stress are indicative of malfunction of endogenous antioxidant capacity. Numerous efforts were made to design and synthesize biologically active antioxidants and free oxygen radical scavenging substances that could improve the endogenous antioxidant status. The antioxidant and reactive-oxygen-species-scavenging activity of STB was well demonstrated in many in vitro and in vivo studies. These properties of STB seem to be closely related to its beneficial effects in models of oxidative-stress-involving pathologies, including myocardial infarction, stroke, neurodegenerative disorders, hypoxic-ischemic tissue injury, diabetic complications, chronic inflammation, etc. STB has a good affinity to lipids and exerts its protective activity against free-radical-mediated damage by preventing lipid peroxidation. Rather than interacting with the radicals initiating lipid peroxidation, STB was shown to act in its propagation stage via scavenging peroxyl and/or alkoxyl radicals. STB was also found to protect proteins, predominantly by a mechanism involving protection of thiol groups and by preventing oxidation of amino acids. The first findings on antioxidant and pharmacodynamic effects of STB, tested in a variety of biological models, were summarized in 1998. Recently, chemical modification of STB, which we considered as the leading structure, led to the synthesis of pyridoindole derivatives with significantly increased intrinsic antiradical activity and overall antioxidant efficacy compared to the parental molecule. The present paper provides a complete overview of the literature published since 1998 on both STB and STB congeners. Moreover, appropriate structural modifications of STB provided the opportunity to modulate lipophilicity and acidobasic behavior, thus optimizing bioavailability of the novel derivatives and attenuating their unwanted sideeffects, with the result of decreased toxicity. Hence, STB congeners might be prospectively used as medicinal antioxidants, i.e. remedies effective in conditions involving oxidative stress-mediated injury.

Biomarkers of Oxidative Stress in Breast Cancer.

Abstract INTRODUCTIONDespite significant improvements in cancer diagnosis and treatment, approximately one-quarter of breast cancer patients will die of their disease. Oxidative stress has been implicated as a contributory factor in the development of breast cancer. Reactive oxygen species can initiate lipid peroxidation, resulting in generation of reactive secondary products which can induce oxidative DNA damage and mutations in the p53 tumour suppressor gene, which is one of the most frequent mutations associated with breast cancer development. Oxidative stress has also been associated with activation of transcription factors and tamoxifen resistance. The aim of the present study was to identify the levels of lipid peroxdation products; malondialdehyde and 8-iso-Prostaglandin F2α (8-iso-PGF2α), in patients with primary operable breast cancer, and to correlate these levels with pathological factors of disease including tumour grade, ER and HER2 status and also Nottingham prognostic index (NPI) status.METHODS:89 patients with primary operable breast cancer and 10 healthy subjects were studied. Plasma levels of MDA (total and free) and 8-iso-PGF2α were measured.RESULTS:The majority of patients were over 50 years (87%), had grade II/III tumours (68%), were axillary lymph node positive (41%) and had ER-positive tumours (82%). Compared to the control, patients had higher levels of total MDA (p<0.001), free MDA (p<0.001), and 8-iso-PGF2α (p<0.001). Both free (p<0.05) and total MDA (p=0.001) were significantly correlated with increasing tumour grade. Furthermore, total MDA levels were also associated with increased tumour size (p<0.05) and ER-negative tumours (p<0.05). Taken together, both total (p<0.001) and free (p <0.05) MDA were significantly associated with higher NPI categories. 8-iso-PGF2α showed only a correlation with increasing age (p<0.05)CONCLUSION:The present study shows that patients with breast cancer have evidence of increased levels of oxidative stress. Furthermore, MDA concentration was significantly associated with conventional markers of poor prognosis. This data suggests oxidative stress may be involved in tumour progression to a more aggressive phenotype. Thus MDA maybe a useful marker of tumour associated oxidative damage and may provide a promising marker for risk prediction and targets for preventative measures in breast cancer patients. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2141.

Oxidizability of unsaturated fatty acids and of a non-phenolic lignin structure in the manganese peroxidase-dependent lipid peroxidation system

Unsaturated fatty acids have been proposed to mediate the oxidation of recalcitrant, non-phenolic lignin structures by fungal manganese peroxidases (MnP), but their precise role remains unknown. We investigated the oxidizability of three fatty acids with varying degrees of polyunsaturation (linoleic, linolenic, and arachidonic acids) by measuring conjugated dienes formation when lipid peroxidation was initiated either by MnP in the presence of Mn(II) or by chelated Mn(III). An inverse relationship between the degree of fatty acid unsaturation and the rate of peroxidation was found in both cases, but we also noted some differences between the two types of reaction. With MnP/Mn(II), the reaction developed slowly and resulted in sustained lipid peroxidation as determined by the formation of late-stage fatty acid degradation products. By contrast, the reaction with chelated Mn(III) was very rapid and did not result in the formation of these late-stage products, which suggests that this system failed to propagate the sustained radical chain reaction that is characteristic of complete lipid peroxidation. All three polyunsaturated fatty acids supported the co-oxidation of a non-phenolic lignin model compound by MnP, again showing an inverse relationship between the degree of unsaturation and reactivity, but chelated Mn(III) by itself supported only very low levels of fatty acid-mediated lignin model oxidation. These parallels in fatty acid reactivity are consistent with a reaction scheme in which Mn(III) acts as the proximal oxidant that initiates lipid peroxidation by MnP, thus generating fatty acid-derived radicals which in turn oxidize lignin structures. However, the results also suggest that the initial peroxyl radicals formed may not be the ligninolytic oxidants in this system. Instead, other radical oxidants produced during late-stage reactions of lipid peroxidation may be required.

Evaluation of the free radical scavenging activity and radioprotective efficacy of Grewiaasiatica fruit

The radioprotective effect of Grewia asiatica fruit (GAE) which contains anthocyanin-type cyanidin3-glucoside, vitamins C and A, minerals, carotenes and dietary fibre was studied. For the studySwiss albino mice were divided into five groups: (1) control (vehicle treated); (2) GAE treated (700 mg kg−1 day−1 for 15 days);(3) irradiated (5 Gy); (4) GAE+irradiated and (5) irradiated+GAE treated. The irradiation of animals resulted in a significant elevation of lipid peroxidationin terms of thiobarbituric acid reactive substances (TBARS) content and depletion inglutathione (GSH) and protein levels at all intervals studied, namely 1–30 days,in comparison to the control group. Treatment of mice with GAE before andafter irradiation caused a significant depletion in TBARS content followed by asignificant elevation in GSH and protein concentration in the intestine and testis ofmice at all post-irradiation autopsy intervals in comparison to irradiated mice.Significant protection of DNA and RNA in testis was also noticed. GAE wasfound to have strong radical scavenging activity in 2,2-diphenyl-1-picrylhydrazyl (DPPH*)and O2− assays and also showed in vitro radioprotective activity in protein carbonyl assay in adose-dependent manner. The above results prove the radioprotective efficacy ofGAE.

Photodegradation Mechanism of Nonsteroidal Anti-Inflammatory Drugs Containing Thiophene Moieties: Suprofen and Tiaprofenic Acid

The photodegradation of nonsteroid anti-inflammatory drugs suprofen, 2-[4-(2-thienoyl)phenyl]propionic acid, and tiaprofenic acid, 2-(5-benzoyl-2-thienyl)propanoic acid, is studied by means of density functional theory. Besides the redox properties of the neutral species, we report on absorption spectra and degradation pathways involving excitation, intersystem crossing to the T(1) state, and spontaneous decarboxylation of the deprotonated species of each drug. The energetics and properties of the suprofen and tiaprofenic acid systems are found to be very similar to those of the highly photolabile benzyl analogue ketoprofen. Mechanisms leading to the formation of a closed-shell decarboxylated ethyl species, as well as peroxyl radicals capable of initiating lipid peroxidation reactions, are discussed.

Isolation, characterization and antioxidative effect of phyllanthin against CCl 4-induced toxicity in HepG2 cell line

The present study was an attempt to investigate the hepatoprotective and antioxidative property of Phyllanthus amarus ( P. amarus) extract and phyllanthin. Phyllanthin, one of the active lignin present in this plant species was isolated from the aerial parts, by silica gel column chromatography employing gradient elution with hexane–ethyl acetate solvent mixture. It was obtained in high yields (1.23%), compared to reported procedures and the purity was ascertained by HPTLC and reversed-phase HPLC analysis. Characterization of phyllanthin was done by mp, UV–Visible spectrophotometry, elemental analysis, FT-IR, 1H NMR, 13C NMR and mass spectral analysis. Free radical scavenging activity of P. amarus extract and phyllanthin was also examined using DPPH assay. The protective effect of P. amarus extract and phyllanthin was studied on CCl 4-induced toxicity in human hepatoma HepG2 cell line. The results indicated that CCl 4 treatment caused a significant decrease in cell viability. In addition, the toxin treatment initiated lipid peroxidation (LPO), caused leakage of enzymes like alanine transaminase (ALT) and lactate dehydrogenase (LDH) with a significant decrease in glutathione (GSH) levels. It was observed that phyllanthin effectively alleviated the changes induced by CCl 4 in a concentration-dependent manner, with much smaller strengths as compared to P. amarus extract.

Effects of positive iron status at a cellular level.

The human body is not equipped to eliminate excess iron. As a result, cells continuously store excess absorbed iron in a complex with the protein ferritin. This poses no great threat under normal conditions. However, under certain disease conditions, oxidative processes cause iron to be mobilized and released as Fe(II). This iron is capable of initiating lipid peroxidation, which can lead to loss of membrane structure and function.

Fe 2+ and Fe 3+ initiated peroxidation of sonicated and non-sonicated liposomes made of retinal lipids in different aqueous media

Retina is highly susceptible to oxidative damage due to its high content of polyunsaturated fatty acids (PUFAs), mainly docosahexaenoic acid (22:6 n3). Lipid peroxidation process is thought to be involved in many physiological and pathological events. Many model membranes can be used to learn more about issues that cannot be studied in biological membranes. Sonicated liposomes (SL) and non-sonicated liposomes (NSL) prepared with lipids isolated from bovine retina and characterized by dynamic light-scattering, were submitted to lipid peroxidation, under air atmosphere at 22 °C, with Fe 2+ or Fe 3+ as initiator, in different aqueous media. Conjugated dienes and trienes, determined by absorption at 234 and 270 nm respectively, and thiobarbituric acid-reactive substances were measured as a function of time. Peroxidation of SL or NSL initiated with 25 μM FeSO 4 in 20 mM Tris–HCl pH 7.4 resulted in an increase in TBARS production after a lag phase of 60 min. Incubation of both types of liposomes in water resulted in shortening of the lag phase at 30 min. When lipid peroxidation was performed in 0.15 M NaCl, lag phase completely disappeared. On the other hand, FeCl 3 (25 μM) induced a limited production of TBARS only just after 30 min of incubation. When Fe 2+- or Fe 3+-lipid peroxidation of both types of liposomes was carried out in water or 0.15 M NaCl, formation of conjugated dienes and conjugated trienes were higher than in reactions carried out in 20 mM Tris–HCl pH 7.4. Our results established that both liposome types were susceptible to Fe 2+- and Fe 3+-initiated lipid peroxidation. However, Fe 2+ showed a clearly enhanced effect on peroxidation rate and steady state concentration of oxidation products. We verified that peroxidation of liposomes made of retinal lipids is affected not only by type of initiator but also by aqueous media. This model constitutes a useful system to study formation of lipid peroxidation intermediaries and products in an aqueous environment.

Substrate oxidation sites in versatile peroxidase and other basidiomycete peroxidases

Versatile peroxidase (VP) is defined by its capabilities to oxidize the typical substrates of other basidiomycete peroxidases: (i) Mn(2+), the manganese peroxidase (MnP) substrate (Mn(3+) being able to oxidize phenols and initiate lipid peroxidation reactions); (ii) veratryl alcohol (VA), the typical lignin peroxidase (LiP) substrate; and (iii) simple phenols, which are the substrates of Coprinopsis cinerea peroxidase (CIP). Crystallographic, spectroscopic, directed mutagenesis, and kinetic studies showed that these 'hybrid' properties are due to the coexistence in a single protein of different catalytic sites reminiscent of those present in the other basidiomycete peroxidase families. Crystal structures of wild and recombinant VP, and kinetics of mutated variants, revealed certain differences in its Mn-oxidation site compared with MnP. These result in efficient Mn(2+) oxidation in the presence of only two of the three acidic residues forming its binding site. On the other hand, a solvent-exposed tryptophan is the catalytically-active residue in VA oxidation, initiating an electron transfer pathway to haem (two other putative pathways were discarded by mutagenesis). Formation of a tryptophanyl radical after VP activation by peroxide was detected using electron paramagnetic resonance. This was the first time that a protein radical was directly demonstrated in a ligninolytic peroxidase. In contrast with LiP, the VP catalytic tryptophan is not beta-hydroxylated under hydrogen peroxide excess. It was also shown that the tryptophan environment affected catalysis, its modification introducing some LiP properties in VP. Moreover, some phenols and dyes are oxidized by VP at the edge of the main haem access channel, as found in CIP. Finally, the biotechnological interest of VP is discussed.

Antioxidant Effects of Different Extracts from Melissa officinalis, Matricaria recutita and Cymbopogon citratus

Considering the important role of oxidative stress in the pathogenesis of several neurological diseases, and the growing evidence of the presence of compounds with antioxidant properties in the plant extracts, the aim of the present study was to investigate the antioxidant capacity of three plants used in Brazil to treat neurological disorders: Melissa officinalis, Matricaria recutita and Cymbopogon citratus. The antioxidant effect of phenolic compounds commonly found in plant extracts, namely, quercetin, gallic acid, quercitrin and rutin was also examined for comparative purposes. Cerebral lipid peroxidation (assessed by TBARS) was induced by iron sulfate (10 microM), sodium nitroprusside (5 microM) or 3-nitropropionic acid (2 mM). Free radical scavenger properties and the chemical composition of plant extracts were assessed by 1'-1' Diphenyl-2' picrylhydrazyl (DPPH) method and by Thin Layer Chromatography (TLC), respectively. M. officinalis aqueous extract caused the highest decrease in TBARS production induced by all tested pro-oxidants. In the DPPH assay, M. officinalis presented also the best antioxidant effect, but, in this case, the antioxidant potencies were similar for the aqueous, methanolic and ethanolic extracts. Among the purified compounds, quercetin had the highest antioxidant activity followed by gallic acid, quercitrin and rutin. In this work, we have demonstrated that the plant extracts could protect against oxidative damage induced by various pro-oxidant agents that induce lipid peroxidation by different process. Thus, plant extracts could inhibit the generation of early chemical reactive species that subsequently initiate lipid peroxidation or, alternatively, they could block a common final pathway in the process of polyunsaturated fatty acids peroxidation. Our study indicates that M. officinalis could be considered an effective agent in the prevention of various neurological diseases associated with oxidative stress.

P-Hydroxycinnamic Acids as Natural Mediators for Laccase Oxidation of Recalcitrant Compounds

The capabilities of p-coumaric acid (PCA), ferulic acid (FA), and sinapic acid (SA) as laccase mediators are compared in oxidation of industrial dyes and polycyclic aromatic hydrocarbons (PAH). SA behaved as highly efficient mediator in decolorization of dyes, including the recalcitrant Reactive Black 5. This mediating capacity was related to the specificity constant of the enzyme oxidizing this p-hydroxycinnamic acid, which was 16 times higher than for the typical substrate 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS). The kinetics of ABTS oxidation by laccase in the presence of p-hydroxycinnamic acids suggested that the stable phenoxyl radical of a SA transformation product acts as laccase mediator. On the other hand, FA and, especially PCA, easily mediated benzo[a]pyrene oxidation, the latter also promoting the oxidation of the more recalcitrant phenanthrene. Phenanthrene transformation by laccase-PCA was enhanced by Tween 80. This fact, together with the detection of TBARS (thiobarbituric acid-reactive-substances) from unsaturated fatty acids, revealed that laccase can also initiate lipid peroxidation reactions in the presence of p-hydroxycinnamic acids enabling oxidation of the most recalcitrant PAH.

The cold but not hard fats in ectotherms: consequences of lipid restructuring on susceptibility of biological membranes to peroxidation, a review

The production of reactive oxygen species is a regular feature of life in the presence of oxygen. Some reactive oxygen species possess sufficient energy to initiate lipid peroxidation in biological membranes, self-propagating reactions with the potential to damage membranes by altering their physical properties and ultimately their function. Two of the most prominent patterns of lipid restructuring in membranes of ectotherms involve contents of polyunsaturated fatty acids and ratios of the abundant phospholipids, phosphatidylcholine and phosphatidylethanolamine. Since polyunsaturated fatty acids and phosphatidylethanolamine are particularly vulnerable to oxidation, it is likely that higher contents of these lipids at low body temperature elevate the inherent susceptibility of membranes to lipid peroxidation. Although membranes from animals living at low body temperatures may be more prone to oxidation, the generation of reactive oxygen species and lipid peroxidation are sensitive to temperature. These scenarios raise the possibility that membrane susceptibility to lipid peroxidation is conserved at physiological temperatures. Reduced levels of polyunsaturated fatty acids and phosphatidylethanolamine may protect membranes at warm temperatures from deleterious oxidations when rates of reactive oxygen species production and lipid peroxidation are relatively high. At low temperatures, enhanced susceptibility may ensure sufficient lipid peroxidation for cellular processes that require lipid oxidation products.

An Iron Enhancer Element in the FTN-1 Gene Directs Iron-dependent Expression in Caenorhabditis elegans Intestine

Ferritin is a ubiquitous protein that sequesters iron and protects cells from iron toxicity. Caenorhabditis elegans express two ferritins, FTN-1 and FTN-2, which are transcriptionally regulated by iron. To identify the cis-acting sequences and proteins required for iron-dependent regulation of ftn-1 and ftn-2 expression, we generated transcriptional GFP reporters corresponding to 5 '-upstream sequences of the ftn-1 and ftn-2 genes. We identified a conserved 63-bp sequence, the iron-dependent element (IDE), that is required for iron-dependent regulation of a ftn-1 GFP reporter in intestine. The IDE contains two GATA-binding motifs and three octameric direct repeats. Site-directed mutagenesis of the GATA sequences, singly or in combination, reduces ftn-1 GFP reporter expression in the intestine. In vitro DNA mobility shift assays show that the intestine-specific GATA protein ELT-2 binds to both GATA sequences. Inhibition of ELT-2 function by RNA interference blocks ftn-1 GFP reporter expression in vivo. Insertion of the IDE into the promoter region of a heterologous reporter activates iron-dependent transcription in intestine. These data demonstrate that the activation of ftn-1 and ftn-2 transcription by iron requires ELT-2 and that the IDE functions as an iron-dependent enhancer in intestine.

Inhibition of hepatitis C virus replication by peroxidation of arachidonate and restoration by vitamin E

Hepatitis C virus (HCV) is a single-stranded positive-sense RNA virus of the Flaviviridae family. HCV-infected hepatocytes are known to produce reactive oxygen species (ROS), which initiate lipid peroxidation, a reaction that converts polyunsaturated fatty acids, such as arachidonate, into reactive carbonyls that inactivate proteins. To study the effect of lipid peroxidation on HCV replication, we administered arachidonate to Huh7 cells that harbor an HCV replicon (Huh7-K2040 cells). After incubation in medium supplemented with arachidonate but deprived of lipid-soluble antioxidants, the cellular amount of malondialdehyde (MDA), a product of lipid peroxidation, increased markedly in Huh7-K2040 cells but not in parental Huh7 cells that do not harbor an HCV replicon. This increase was followed by a sharp reduction (>95%) in HCV RNA. Both of these events were prevented when cells were treated with vitamin E, a lipid-soluble antioxidant. After prolonged incubation of Huh7-K2040 cells with arachidonate in the absence of lipid-soluble antioxidants, the amount of MDA decreased after the reduction in the amount of HCV RNA. Thus, in the presence of arachidonate and in the absence of lipid-soluble antioxidants, HCV replication induces lipid peroxidation that reduces the amount of HCV RNA. Our results provide a mechanism for the previous observation that polyunsaturated fatty acids inhibit HCV replication [Kapadia SB, Chisari FV (2005) Proc Natl Acad Sci USA 102:2561-2566], and they suggest that these agents may be effective in inhibiting HCV replication in vivo.

Theoretical Study of Ibuprofen Phototoxicity

The photochemical properties and degradation of the common nonsteroid anti-inflammatory drug ibuprofen is studied by means of hybrid density functional theory. Computed energies and properties of various species show that the deprotonated form dominates at physiological pH, and that the species will not be able to decarboxylate from a singlet excited state. Instead, decarboxylation will occur, with very high efficiency, provided the deprotonated compound can undergo intersystem crossing from an excited singlet to its excited triplet state. In the triplet state, the C-C bond connecting the carboxyl group is elongated, and the CO2 moiety detaches with a free energy barrier of less than 0.5 kcal/mol. Depending on the local environment, the decarboxylated product can then either be quenched through intersystem crossing (involving the possible formation of singlet oxygen) and protonation, or serve as an efficient source for superoxide anions and the formation of a peroxyl radical that will initiate lipid peroxidation.

Abstract 598: Deletion of Microsomal PGE Synthase-1 Decreases Oxidative Stress and Protects Against Abdominal Aortic Aneurysm Formation in Angiotensin II-Infused Mice

Microsomal (m) prostaglandin (PG) E 2 synthase(S)-1, an enzyme that catalyzes the isomerization of the cyclooxygenase (COX) product, PGH 2 , into PGE 2 , is a major source of PGE 2 in vivo . mPGES-1 deletion in mice was found to modulate experimentally evoked pain and inflammation and atherogenesis is retarded in mPGES-1 knockout (KO) mice. The impact of mPGES-1 deletion on formation of angiotensin II (Ang II)-induced abdominal aortic aneurysms (AAA) was studied in mice lacking the low density lipoprotein receptor (LDLR −/− ). AngII infusion increased aortic macrophage recruitment and nitrotyrosine staining while upregulating both mPGES-1 and COX-2 and urinary excretion of the major metabolite of PGE 2 (PGE-M). Deletion of mPGES-1 decreased both the incidence and severity of AAA and depressed excretion of both PGE-M and 8, 12-iso-iPF 2a -VI, which reflects lipid peroxidation in vivo . While Ang II infusion augmented prostaglandin biosynthesis, deletion of mPGES-1 resulted in rediversion to PGD 2 , reflected by its major urinary metabolite. However, deletion of the PGD 2 receptor, DP1, did not affect AAA in Ang II infused LDLR −/− mice. These observations indicate that deletion of mPGES-1 protects against AAA formation by AngII in hyperlipidemic mice, perhaps by decreasing oxidative stress. Inhibition of mPGES-1 may represent an effective treatment to limit aneurysm occurrence and expansion.