Singlet-oxygen-mediated amino acid and protein oxidation: formation of tryptophan peroxides and decomposition products

Elimination of disinfection byproduct formation potential in reclaimed water during solar light irradiation

Ecological storage of reclaimed water in ponds and lakes is widely applied in water reuse. During reclaimed water storage, solar light can degrade pollutants and improve water quality. This study investigated the effects of solar light irradiation on the disinfection byproduct formation potential in reclaimed water, including haloacetonitriles (HANs), trichloronitromethane (TCNM), trihalomethanes (THMs), haloketones (HKs) and chloral hydrate (CH). Natural solar light significantly decreased the formation potential of HANs, TCNM, and HKs in reclaimed water, but had a limited effect on the formation potential of THMs and CH. Ultraviolet (UV) light in solar radiation played a dominant role in the decrease of the formation potential of HANs, TCNM and HKs. Among the disinfection byproducts, the removal kinetic constant of dichloroacetonitrile (DCAN) with irradiation dose was much larger than those for dichloropropanone (1,1-DCP), trichloropropanone (1,1,1-TCP) and TCNM. During solar irradiation, fluorescence spectra intensities of reclaimed water also decreased significantly. The removal of tyrosine (Tyr)-like and tryptophan (Trp)-like protein fluorescence spectra intensity volumes was correlated to the decrease in DCAN formation potential. Solar irradiation was demonstrated to degrade Trp, Tyr and their DCAN formation potential. The photolysis products of Trp after solar irradiation were detected as kynurenine and tryptamine, which had chloroform, CH and DCAN formation potential lower than those of Trp.

Evaluation of Antioxidant or Prooxidant Properties of Selected Amino Acids Using In Vitro Assays and in Oil-in-Water Emulsions Under Riboflavin Sensitization

The antioxidant properties of selected amino acids were tested using in vitro assays and oil-in-water (O/W) emulsions under riboflavin (RF) photosensitization. Headspace oxygen content, lipid hydroperoxides, and conjugated dienes were determined for the degree of oxidation. Riboflavin photosensitization was adapted as the oxidation driving force. In vitro assays showed that cysteine had the highest antioxidant properties followed by tryptophan and tyrosine. However, in O/W emulsions under RF photosensitization, tyrosine inhibited lipid oxidation whereas tryptophan acted as a prooxidant. Tryptophan accelerated the rates of oxidation in O/W emulsion without RF. The antioxidant properties of amino acids differed depending on the antioxidant determination methods, oxidation driving forces, and food matrices.

Protein oxidation and peroxidation

Proteins are major targets for radicals and two-electron oxidants in biological systems due to their abundance and high rate constants for reaction. With highly reactive radicals damage occurs at multiple side-chain and backbone sites. Less reactive species show greater selectivity with regard to the residues targeted and their spatial location. Modification can result in increased side-chain hydrophilicity, side-chain and backbone fragmentation, aggregation via covalent cross-linking or hydrophobic interactions, protein unfolding and altered conformation, altered interactions with biological partners and modified turnover. In the presence of O2, high yields of peroxyl radicals and peroxides (protein peroxidation) are formed; the latter account for up to 70% of the initial oxidant flux. Protein peroxides can oxidize both proteins and other targets. One-electron reduction results in additional radicals and chain reactions with alcohols and carbonyls as major products; the latter are commonly used markers of protein damage. Direct oxidation of cysteine (and less commonly) methionine residues is a major reaction; this is typically faster than with H2O2, and results in altered protein activity and function. Unlike H2O2, which is rapidly removed by protective enzymes, protein peroxides are only slowly removed, and catabolism is a major fate. Although turnover of modified proteins by proteasomal and lysosomal enzymes, and other proteases (e.g. mitochondrial Lon), can be efficient, protein hydroperoxides inhibit these pathways and this may contribute to the accumulation of modified proteins in cells. Available evidence supports an association between protein oxidation and multiple human pathologies, but whether this link is causal remains to be established.

Protein profiles of Escherichia coli and Staphylococcus warneri are altered by photosensitization with cationic porphyrins

Oxidative stress induced by photodynamic treatment of microbial cells causes irreversible damages to vital cellular components such as proteins. Photodynamic inactivation (PDI) of bacteria, a promising therapeutic approach for the treatment of superficial and localized skin and oral infections, can be achieved by exciting a photosensitizing agent with visible light in an oxygenated environment. Although some studies have addressed the oxidative alterations of PDI in bacterial proteins, the present study is the first to compare the electrophoretic profiles of proteins of Gram-positive and Gram-negative bacteria, having two structurally different porphyrins, with different kinetics of photoinactivation. The cationic porphyrins 5,10,15-tris(1-methylpyridinium-4-yl)-20-(pentafluorophenyl)porphyrin tri-iodide (Tri-Py(+)-Me-PF) and 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin tetra-iodide (Tetra-Py(+)-Me) were used to photosensitize Escherichia coli and Staphylococcus warneri upon white light irradiation at an irradiance of 4.0 mW cm(-2). After different photosensitization periods, proteins were extracted from bacteria and analyzed using one-dimensional SDS-PAGE. Apparent molecular weights and band intensities were determined after an irradiation period corresponding to a reduction of 4 log10 in cell viability. After photodynamic treatment, there was a general loss of bacterial proteins, assigned to large-scale protein degradation. Protein loss was more pronounced after PDI with Tri-Py(+)-Me-PF in both bacteria. There was also an increase in the concentration of some proteins as well as an increase in the molecular weight of other proteins. We show that proteins of E. coli and S. warneri are important targets of PDI. Although there is an attempt of cellular response to the PDI-induced damage by overexpression of a limited number of proteins, the damage is lethal. Our results show that changes occurring in the protein pattern during photodynamic treatment are different with the two photosensitizers, which helps to explain the different inactivation kinetics of the two bacteria. SDS-PAGE is a rational approach to assign the type of cellular response to stress that is being induced in the cells.

Ab-initio HF and density functional theory investigations on the synthesis mechanism, conformational stability, molecular structure and UV spectrum of N’-Formylkynurenine

Tryptophan methyl ester (Trp-ME) degrades with singlet oxygen and produce compounds which are photosensitizers and may react to form other derivatives such as N’-Formylkynurénine (NFK) and kynurenine, which are the final products of this oxidation. In order to study and optimize the molecular structure of NFK and determine its different thermodynamic properties, we performed a conformational analysis by DFT/B3LYP method with 3-21G basis set. Six most stable conformations were observed through the analysis of the potential energy surfaces, obtained by a relaxed scan of the dihedral angles.

The most stable form of NFK has been registered for D[Formula: see text], D[Formula: see text], D[Formula: see text], D[Formula: see text], D[Formula: see text], and D[Formula: see text]. The study was conducted by HF and DFT/B3LYP with 6-31G(d,p), 6-3[Formula: see text](d,p) and 6-31[Formula: see text](d,p) basis sets, on the optimized geometry of the most stable conformation and its thermodynamic and orbital properties. Two absorption bands were recorded at [Formula: see text][Formula: see text]nm and at [Formula: see text][Formula: see text]nm and were also determined by TD-DFT method. They showed good agreement with the UV experimental spectrum which confirms that it is a powerful tool to determine the dynamic and static properties of molecules. The surface of the electrostatic potential (ESP) of the NFK was also analyzed.

Time and dose dependent effects of oxidative stress induced by cumene hydroperoxide in neuronal excitability of rat motor cortex neurons

It has been claimed that oxidative stress and the production of reactive oxygen radicals can contribute to neuron degeneration and might be one factor in the development of different neurological diseases. In our study, we have attempted to clarify how oxidative damage induces dose dependent changes in functional membrane properties of neurons by means of whole cell patch clamp techniques in brain slices from young adult rats. Our research demonstrates physiological changes in membrane properties of pyramidal motor cortex neurons exposed to 3 concentrations of cumene hydroperoxide (CH; 1, 10 and 100μM) during 30min. Results show that oxidative stress induced by CH evokes important changes, in a concentration and time dependent manner, in the neuronal excitability of motor cortex neurons of the rat: (i) Low concentration of the drug (1μM) already blocks inward rectifications (sag) and decreases action potential amplitude and gain, a drug concentration which has no effects on other neuronal populations, (ii) 10μM of CH depresses the excitability of pyramidal motor cortex neurons by decreasing input resistance, amplitude of the action potential, and gain and maximum frequency of the repetitive firing discharge, and (iii) 100μM completely blocks the capability to produce repetitive discharge of action potentials in all cells. Both larger drug concentrations and/or longer times of exposure to CH narrow the current working range. This happens because of the increase in the rheobase, and the reduction of the cancelation current. The effects caused by oxidative stress, including those produced by the level of lipid peroxidation, are practically irreversible and, this, therefore, indicates that neuroprotective agents should be administered at the first symptoms of alterations to membrane properties. In fact, the pre-treatment with melatonin, acting as an antioxidant, prevented the lipid peroxidation and the physiological changes induced by CH. Larger cells (as estimated by their cell capacitance) were also more susceptible to oxidative stress. Our results provide previously unavailable observations that large size and high sensitivity to oxidative stress (even at low concentrations) make pyramidal neurons of the motor cortex, in particular corticofugal neurons, more susceptible to cell death when compared with other neuronal populations. These results could also shed some light on explaining the causes behind diseases such as Amyotrophic Lateral Sclerosis.

Oxidation of free, peptide and protein tryptophan residues mediated by AAPH-derived free radicals: role of alkoxyl and peroxyl radicals

When AAPH is employed as a free radical source, at low concentrations of free, peptide and protein Trp residues, the oxidation is mostly induced by alkoxyl radicals. However, at high concentrations, both peroxyl and alkoxyl radicals are involved.

Target-selective photo-degradation of AFP-L3 and selective photo-cytotoxicity against HuH-7 hepatocarcinoma cells using an anthraquinone–PhoSL hybrid

A purposefully-designed anthraquinone–Pholiota squarrosa lectin (PhoSL) hybrid effectively degraded α-fetoprotein-L3 (AFP-L3) associated with liver cancer.

Lysozyme Photochemistry as a Function of Temperature. The Protective Effect of Nanoparticles on Lysozyme Photostability

The presence of aromatic residues and their close spatial proximity to disulphide bridges makes hen egg white lysozyme labile to UV excitation. UVB induced photo-oxidation of tryptophan and tyrosine residues leads to photochemical products, such as, kynurenine, N-formylkynurenine and dityrosine and to the disruption of disulphide bridges in proteins. We here report that lysozyme UV induced photochemistry is modulated by temperature, excitation power, illumination time, excitation wavelength and by the presence of plasmonic quencher surfaces, such as gold, and by the presence of natural fluorescence quenchers, such as hyaluronic acid and oleic acid. We show evidence that the photo-oxidation effects triggered by 295 nm at 20°C are reversible and non-reversible at 10°C, 25°C and 30°C. This paper provides evidence that the 295 nm damage threshold of lysozyme lies between 0.1 μW and 0.3 μW. Protein conformational changes induced by temperature and UV light have been detected upon monitoring changes in the fluorescence emission spectra of lysozyme tryptophan residues and SYPRO® Orange. Lysozyme has been conjugated onto gold nanoparticles, coated with hyaluronic acid and oleic acid (HAOA). Steady state and time resolved fluorescence studies of free and conjugated lysozyme onto HAOA gold nanoparticles reveals that the presence of the polymer decreased the rate of the observed photochemical reactions and induced a preference for short fluorescence decay lifetimes. Size and surface charge of the HAOA gold nanoparticles have been determined by dynamic light scattering and zeta potential measurements. TEM analysis of the particles confirms the presence of a gold core surrounded by a HAOA matrix. We conclude that HAOA gold nanoparticles may efficiently protect lysozyme from the photochemical effects of UVB light and this nanocarrier could be potentially applied to other proteins with clinical relevance. In addition, this study confirms that the temperature plays a critical role in the photochemical pathways a protein enters upon UV excitation.

Tripping up Trp: Modification of protein tryptophan residues by reactive oxygen species, modes of detection, and biological consequences

Proteins comprise a majority of the dry weight of a cell, rendering them a major target for oxidative modification. Oxidation of proteins can result in significant alterations in protein molecular mass such as breakage of the polypeptide backbone and/or polymerization of monomers into dimers, multimers, and sometimes insoluble aggregates. Protein oxidation can also result in structural changes to amino acid residue side chains, conversions that have only a modest effect on protein size but can have widespread consequences for protein function. There are a wide range of rate constants for amino acid reactivity, with cysteine, methionine, tyrosine, phenylalanine, and tryptophan having the highest rate constants with commonly encountered biological oxidants. Free tryptophan and tryptophan protein residues react at a diffusion-limited rate with hydroxyl radical and also have high rate constants for reactions with singlet oxygen and ozone. Although oxidation of proteins in general and tryptophan residues specifically can have effects detrimental to the health of cells and organisms, some modifications are neutral, whereas others contribute to the function of the protein in question or may act as a signal that damaged proteins need to be replaced. This review provides a brief overview of the chemical mechanisms by which tryptophan residues become oxidized, presents both the strengths and the weaknesses of some of the techniques used to detect these oxidative interactions, and discusses selected examples of the biological consequences of tryptophan oxidation in proteins from animals, plants, and microbes.

Production of lysozyme and lysozyme-superoxide dismutase dimers bound by a ditryptophan cross-link in carbonate radical-treated lysozyme

Despite extensive investigation of the irreversible oxidations undergone by proteins in vitro and in vivo, the products formed from the oxidation of Trp residues remain incompletely understood. Recently, we characterized a ditryptophan cross-link produced by the recombination of hSOD1-tryptophanyl radicals generated from attack of the carbonate radical produced during the bicarbonate-dependent peroxidase activity of the enzyme. Here, we examine whether the ditryptophan cross-link is produced by the attack of the carbonate radical on proteins other than hSOD1. To this end, we treated hen egg white lysozyme with photolytically and enzymatically generated carbonate radical. The radical yields were estimated and the lysozyme modifications were analyzed by SDS-PAGE, western blot, enzymatic activity and MS/MS analysis. Lysozyme oxidation by both systems resulted in its inactivation and dimerization. Lysozyme treated with the photolytic system presented monomers oxidized to hydroxy-tryptophan at Trp(28) and Trp(123) and N-formylkynurenine at Trp(28), Trp(62) and Trp(123). Lysozyme treated with the enzymatic system rendered monomers oxidized to N-formylkynurenine at Trp(28). The dimers were characterized as lysozyme-Trp(28)-Trp(28)-lysozyme and lysozyme-Trp(28)-Trp(32)-hSOD1. The results further demonstrate that the carbonate radical is prone to causing biomolecule cross-linking and hence, may be a relevant player in pathological mechanisms. The possibility of exploring the formation of ditryptophan cross-links as a carbonate radical biomarker is discussed.

Anion exchange nanofiber materials activated by daylight with a dual antibacterial effect

Anion exchange polystyrene nanofiber materials (AE) were prepared by electrospinning followed by two-step functionalization of the nanofiber surface by chlorosulfonic acid and ethylendiamine. The photoactive character of these materials was introduced through adsorption of the tetra-anionic 5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin photosensitizer (TPPS-AE) on the nanofiber surface or by encapsulation of the nonpolar 5,10,15,20-tetraphenylporphyrin photosensitizer (AE(TPP)) into the nanofibers. Anion exchange nanofiber materials with porphyrins are characterized by a high ion-exchange capacity, photogeneration of singlet oxygen O2((1)Δg), and singlet oxygen-sensitized delayed fluorescence. Due to the photogeneration of cytotoxic O2((1)Δg), the nanofibers exhibited oxidation of the external substrates in aqueous solution and an efficient antibacterial effect when activated by simulated daylight. Adsorption of both TPPS and I(-) on the surface of AE led to the formation of more efficient I-TPPS-AE materials. Rapid photooxidation of I(-) by O2((1)Δg), and the formation of another cytotoxic species, I3(-), on the surface of the nanofibers were responsible for the increased antibacterial properties of I-TPPS-AE and the prolonged antibacterial effect in the dark.

Recent advances in the use of mass spectrometry to examine structure/function relationships in photosystem II

Tandem mass spectrometry often coupled with chemical modification techniques, is developing into increasingly important tool in structural biology. These methods can provide important supplementary information concerning the structural organization and subunit make-up of membrane protein complexes, identification of conformational changes occurring during enzymatic reactions, identification of the location of posttranslational modifications, and elucidation of the structure of assembly and repair complexes. In this review, we will present a brief introduction to Photosystem II, tandem mass spectrometry and protein modification techniques that have been used to examine the photosystem. We will then discuss a number of recent case studies that have used these techniques to address open questions concerning PS II. These include the nature of subunit-subunit interactions within the phycobilisome, the interaction of phycobilisomes with Photosystem I and the Orange Carotenoid Protein, the location of CyanoQ, PsbQ and PsbP within Photosystem II, and the identification of phosphorylation and oxidative modification sites within the photosystem. Finally, we will discuss some of the future prospects for the use of these methods in examining other open questions in PS II structural biochemistry.

Spin trapping combined with quantitative mass spectrometry defines free radical redistribution within the oxidized hemoglobin:haptoglobin complex

Extracellular or free hemoglobin (Hb) accumulates during hemolysis, tissue damage, and inflammation. Heme-triggered oxidative reactions can lead to diverse structural modifications of lipids and proteins, which contribute to the propagation of tissue damage. One important target of Hb׳s peroxidase reactivity is its own globin structure. Amino acid oxidation and crosslinking events destabilize the protein and ultimately cause accumulation of proinflammatory and cytotoxic Hb degradation products. The Hb scavenger haptoglobin (Hp) attenuates oxidation-induced Hb degradation. In this study we show that in the presence of hydrogen peroxide (H2O2), Hb and the Hb:Hp complex share comparable peroxidative reactivity and free radical generation. While oxidation of both free Hb and Hb:Hp complex generates a common tyrosine-based free radical, the spin-trapping reaction with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) yields dissimilar paramagnetic products in Hb and Hb:Hp, suggesting that radicals are differently redistributed within the complex before reacting with the spin trap. With LC-MS(2) mass spectrometry we assigned multiple known and novel DMPO adduct sites. Quantification of these adducts suggested that the Hb:Hp complex formation causes extensive delocalization of accessible free radicals with drastic reduction of the major tryptophan and cysteine modifications in the β-globin chain of the Hb:Hp complex, including decreased βCys93 DMPO adduction. In contrast, the quantitative changes in DMPO adduct formation on Hb:Hp complex formation were less pronounced in the Hb α-globin chain. In contrast to earlier speculations, we found no evidence that free Hb radicals are delocalized to the Hp chain of the complex. The observation that Hb:Hp complex formation alters free radical distribution in Hb may help to better understand the structural basis for Hp as an antioxidant protein.

Practical problems when using ABTS assay to assess the radical-scavenging activity of peptides: Importance of controlling reaction pH and time

Effects of reaction pH and time on the antioxidant behaviors of Tyr, Trp, Cys, and their related peptides (Tyr-Gly, Tyr-Glu, Tyr-Lys, Trp-Gly, Trp-Glu, Trp-Lys, Cys-Gly and Cys-Gly) in ABTS assay were investigated. Results showed that all these amino acids and peptides displayed a biphasic kinetic pattern with a fast initial step and a slow secondary step. The initial reaction rates of Tyr, Trp and their related peptides were strongly dependent on pH, while those of Cys and Cys-containing peptides were unaffected by pH. They failed to reach equilibrium over the short incubation period of 6-10 min typically used in this assay. Longer incubation time was needed for most of the peptides to approach equilibrium at lower pH. The observed biphasic kinetic pattern as well as the high TEAC values for these amino acids and peptides, could be a result of combined antioxidant behaviors of themselves plus the generated reaction products.

Prevention of degradation of the natural high potency sweetener (2R,4R)-monatin in mock beverage solutions

Exposure of the naturally-occurring sweetener monatin to light and metal ions results in loss of both parent monatin and total indole (monatin plus monatin lactone/lactam) in mock beverage solutions, with an accompanying decrease in sweetness. In this study potential protective strategies to prevent degradation were investigated. Metal ion chelating resin, or the chelators EDTA and desferrioxamine decreased monatin and indole loss for solutions kept either in darkness or exposed to light. Tannic acid and Chinese bayberry extract both afforded protection, but this did not arise from a light filtering effect. Plastics with defined absorbance characteristics provided protection with this being wavelength dependent; yellow transparent PET plastic was most effective. The contribution of these interventions (metal ion removal/binding; antioxidant; light absorption) was additive, with combinations providing the greatest protective effect against monatin and indole loss. These results indicate that it is possible to minimise monatin degradation by appropriate choices of treatments, additives and container.

Oxidative stress induced by cumene hydroperoxide evokes changes in neuronal excitability of rat motor cortex neurons

Oxidative stress and the production of reactive oxygen radicals play a key role in neuronal cell damage. This paper describes an in vitro study that explores the neuronal responses to oxidative stress focusing on changes in neuronal excitability and functional membrane properties. This study was carried out in pyramidal cells of the motor cortex by applying whole-cell patch-clamp techniques on brain slices from young adult rats. Oxygen-derived free radical formation was induced by bath application of 10μM cumene hydroperoxide (CH) for 30min. CH produced marked changes in the electrophysiological properties of neurons (n=30). Resting membrane potential became progressively depolarized, as well as depolarization voltage, with no variations in voltage threshold. Membrane resistance showed a biphasic behavior, increasing after 5min of drug exposure and then it started to decrease, even under control values, after 15 and 30min. At the same time, changes in membrane resistance produced compensatory variations in the rheobase. The amplitude of the action potentials diminished and the duration increased progressively over time. Some of the neurons under study also lost their ability to discharge action potentials in a repetitive way. Most of the neurons, however, kept their repetitive discharge even though their maximum frequency and gain decreased. Furthermore, cancelation of the repetitive firing discharge took place at intensities that decreased with time of exposure to CH, which resulted in a narrower working range. We can conclude that oxidative stress compromises both neuronal excitability and the capability of generating action potentials, and so this type of neuronal functional failure could precede the neuronal death characteristics of many neurodegenerative diseases.

Photosensitisation studies of silicone polymer doped with methylene blue and nanogold for antimicrobial applications

2 nm gold nanoparticle (AuNP) and methylene blue (MB) incorporated into medical-grade silicone polymer for antimicrobial applications.

Ethyl 3,4-dihydroxy benzoate, a unique preconditioning agent for alleviating hypoxia-mediated oxidative damage in L6 myoblasts cells

The importance of hypoxia inducible factor (HIF) as the master regulator of hypoxic responses is well established. Oxygen-dependent prolyl hydroxylase domain enzymes (PHDs) negatively regulate HIF directing it to the path of degradation under normoxia and are, consequently, attractive therapeutic targets. Inhibition of PHDs might upregulate beneficial HIF-mediated processes. In this study, we have examined the efficacy of PHD inhibitor ethyl 3,4-dihydroxy benzoate (EDHB) in affording protection against hypoxia-induced oxidative damage in L6 myoblast cells. L6 cells were exposed to hypoxia (0.5 % O2) after preconditioning with EDHB for different times. Levels of HIF-1α, oxidative stress and antioxidant status were measured after hypoxia exposure. Preconditioning with EDHB significantly improved cellular viability, and the diminished levels of protein oxidation and malondialdehyde indicated a decrease in oxidative stress when exposed to hypoxia. EDHB treatment also conferred enhanced anti-oxidant status, as there was an increase in the levels of glutathione and antioxidant enzymes like superoxide dismutase and glutathione peroxidase. Further, augmentation of the levels of HIF-1α boosted protein expression of antioxidative enzyme heme-oxygenase I. There was enhanced expression of metallothioneins which also have antioxidant, anti-inflammatory properties. These results thus accentuate the potential cytoprotective efficacy of EDHB against hypoxia-induced oxidative damage.

Protein oxidation: identification and utilisation of molecular markers to differentiate singlet oxygen and hydroxyl radical-mediated oxidative pathways

The effect of reactive oxidation species (ROS) on tryptophan or tyrosine was investigated by qualitatively determining the major detectable oxidation products generated by hydroxyl radicals, produced by the Fenton process, or singlet oxygen, generated by exposure to green light in the presence of Rose Bengal, on these photosensitive amino acids in synthetic pentapeptides. Based on mass spectrometric analysis it would appear that the hydroxyl radical favours a pathway leading to the formation of tryptophandione-based products from tryptophan. In contrast singlet oxygen attack appears to favour the formation of kynurenine-type products from tryptophan. Specific oxidative products observed proteomically are therefore potentially able to discriminate between predominant ROS-mediated pathways. To validate these findings, a keratin-enriched extract was exposed to UVB light under aqueous conditions. The observation of the conversion of tryptophan to hydroxytryptophan in marker peptides, and the absence of singlet-oxygen specific modifications, suggested that under these conditions oxidative degradation occurred primarily via hydroxyl radical attack. These observations provide the first direct proteomic evidence of the dominant photodegradation pathways in wet wool.

A facile means for the identification of indolic compounds from plant tissues

The bulk of indole-3-acetic acid (IAA) in plants is found in the form of conjugated molecules, yet past research on identifying these compounds has largely relied on methods that were both laborious and inefficient. Using recent advances in analytical instrumentation, we have developed a simple yet powerful liquid chromatography-mass spectrometry (LC-MS)-based method for the facile characterization of the small IAA conjugate profile of plants. The method uses the well-known quinolinium ion (m/z 130.0651) generated in MS processes as a signature with high mass accuracy that can be used to screen plant extracts for indolic compounds, including IAA conjugates. We reinvestigated Glycine max (soybean) for its indoles and found indole-3-acetyl-trytophan (IA-Trp) in addition to the already known indole-3-acetyl-aspartic acid (IA-Asp) and indole-3-acetyl-glutamic acid (IA-Glu) conjugates. Surprisingly, several organic acid conjugates of tryptophan were also discovered, many of which have not been reported in planta before. These compounds may have important physiological roles in tryptophan metabolism, which in turn can affect human nutrition. We also demonstrated the general applicability of this method by identifying indolic compounds in different plant tissues of diverse phylogenetic origins. It involves minimal sample preparation but can work in conjunction with sample enrichment techniques. This method enables quick screening of IAA conjugates in both previously characterized as well as uncharacterized species, and facilitates the identification of indolic compounds in general.

Tryptophan oxidation in proteins exposed to thiocyanate-derived oxidants

Human defensive peroxidases, including lactoperoxidase (LPO) and myeloperoxidase (MPO), are capable of catalyzing the oxidation of halides (X(-)) by H2O2 to give hypohalous acids (HOX) for the purpose of cellular defense. Substrate selectivity depends upon the relative abundance of the halides, but the pseudo-halide thiocyanate (SCN(-)) is a major substrate, and sometimes the exclusive substrate, of all defensive peroxidases in most physiologic fluids. The resulting hypothiocyanous acid (HOSCN) has been implicated in cellular damage via thiol oxidation. While thiols are believed to be the primary target of HOSCN in vivo, Trp residues have also been implicated as targets for HOSCN. However, the mechanism involved in HOSCN-mediated Trp oxidation was not established. Trp residues in proteins appeared to be susceptible to oxidation by HOSCN, whereas free Trp and Trp residues in small peptides were found to be unreactive. We show that HOSCN-induced Trp oxidation is dependent on pH, with oxidation of free Trp, and Trp-containing peptides observed when the pH is below 2. These conditions mimic those employed previously to precipitate proteins after treatment with HOSCN, which accounts for the discrepancy in the results reported for proteins versus free Trp and small peptides. The reactant in these cases may be thiocyanogen ((SCN)2), which is produced by comproportionation of HOSCN and SCN(-) at low pH. Reaction of thiocyanate-derived oxidants with protein Trp residues at low pH results in the formation of a number of oxidation products, including mono- and di-oxygenated derivatives, which are also formed with other hypohalous acids. Our data suggest that significant modification of Trp by HOSCN in vivo is likely to have limited biological relevance.

Analysis of protein carbonylation--pitfalls and promise in commonly used methods

Oxidation of proteins has received a lot of attention in the last decades due to the fact that they have been shown to accumulate and to be implicated in the progression and the pathophysiology of several diseases such as Alzheimer, coronary heart diseases, etc. This has also resulted in the fact that research scientists are becoming more eager to be able to measure accurately the level of oxidized protein in biological materials, and to determine the precise site of the oxidative attack on the protein, in order to get insights into the molecular mechanisms involved in the progression of diseases. Several methods for measuring protein carbonylation have been implemented in different laboratories around the world. However, to date no methods prevail as the most accurate, reliable, and robust. The present paper aims at giving an overview of the common methods used to determine protein carbonylation in biological material as well as to highlight the limitations and the potential. The ultimate goal is to give quick tips for a rapid decision making when a method has to be selected and taking into consideration the advantage and drawback of the methods.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Real-time measurements of amino acid and protein hydroperoxides using coumarin boronic acid

Hydroperoxides of amino acid and amino acid residues (tyrosine, cysteine, tryptophan, and histidine) in proteins are formed during oxidative modification induced by reactive oxygen species. Amino acid hydroperoxides are unstable intermediates that can further propagate oxidative damage in proteins. The existing assays (oxidation of ferrous cation and iodometric assays) cannot be used in real-time measurements. In this study, we show that the profluorescent coumarin boronic acid (CBA) probe reacts with amino acid and protein hydroperoxides to form the corresponding fluorescent product, 7-hydroxycoumarin. 7-Hydroxycoumarin formation was catalase-independent. Based on this observation, we have developed a fluorometric, real-time assay that is adapted to a multiwell plate format. This is the first report showing real-time monitoring of amino acid and protein hydroperoxides using the CBA-based assay. This approach was used to detect protein hydroperoxides in cell lysates obtained from macrophages exposed to visible light and photosensitizer (rose bengal). We also measured the rate constants for the reaction between amino acid hydroperoxides (tyrosyl, tryptophan, and histidine hydroperoxides) and CBA, and these values (7-23 M(-1) s(-1)) were significantly higher than that measured for H2O2 (1.5 M(-1) s(-1)). Using the CBA-based competition kinetics approach, the rate constants for amino acid hydroperoxides with ebselen, a glutathione peroxidase mimic, were also determined, and the values were within the range of 1.1-1.5 × 10(3) M(-1) s(-1). Both ebselen and boronates may be used as small molecule scavengers of amino acid and protein hydroperoxides. Here we also show formation of tryptophan hydroperoxide from tryptophan exposed to co-generated fluxes of nitric oxide and superoxide. This observation reveals a new mechanism for amino acid and protein hydroperoxide formation in biological systems.

Lipid peroxidation: production, metabolism, and signaling mechanisms of malondialdehyde and 4-hydroxy-2-nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Mechanisms of degradation of the natural high-potency sweetener (2R,4R)-monatin in mock beverage solutions

The sodium, potassium, or mixed sodium/potassium salt of the naturally occurring high-potency sweetener (2R,4R)-monatin, also known by the common name arruva, degrades over time in model beverage solutions in the presence of light. By use of UHPLC, LC-MS/MS, and peroxide assays, it has been demonstrated that degradation is accelerated by UV/visible light and the presence of trace metal ions. Data are presented that are consistent with a role for singlet oxygen (¹O₂), free radicals, and peroxides (both H₂O₂ and organic peroxides) in monatin oxidation. Separation of degradation products by UHPLC/HPLC or LC-MS/MS provided evidence for the formation of hydroxylated and peroxide species formed on the indole ring (mass increases 16 and 32, respectively) as well as multiple ring and side-chain oxidation and scission products. Model oxidation systems using the photosensitizer Rose Bengal as a source of ¹O₂ support the proposed photodegradation pathways.

State-dependent and site-directed photodynamic transformation of HCN2 channel by singlet oxygen

Singlet oxygen acts through a histidine residue to delay HCN channel deactivation and enhance voltage-insensitive current.

Singlet oxygen (¹O₂), which is generated through metabolic reactions and oxidizes numerous biological molecules, has been a useful tool in basic research and clinical practice. However, its role as a signaling factor, as well as a mechanistic understanding of the oxidation process, remains poorly understood. Here, we show that hyperpolarization-activated, cAMP-gated (HCN) channels–which conduct the hyperpolarization-activated current (I_h) and the voltage-insensitive instantaneous current (I_inst), and contribute to diverse physiological functions including learning and memory, cardiac pacemaking, and the sensation of pain–are subject to modification by ¹O₂. To increase the site specificity of ¹O₂ generation, we used fluorescein-conjugated cAMP, which specifically binds to HCN channels, or a chimeric channel in which an in-frame ¹O₂ generator (SOG) protein was fused to the HCN C terminus. Millisecond laser pulses reduced I_h current amplitude, slowed channel deactivation, and enhanced I_inst current. The modification of HCN channel function is a photodynamic process that involves ¹O₂, as supported by the dependence on dissolved oxygen in solutions, the inhibitory effect by a ¹O₂ scavenger, and the results with the HCN2-SOG fusion protein. Intriguingly, ¹O₂ modification of the HCN2 channel is state dependent: laser pulses applied to open channels mainly slow down deactivation and increase I_inst, whereas for the closed channels, ¹O₂ modification mainly reduced I_h amplitude. We identified a histidine residue (H434 in S6) near the activation gate in the pore critical for ¹O₂ modulation of HCN function. Alanine replacement of H434 abolished the delay in channel deactivation and the generation of I_inst induced by photodynamic modification. Our study provides new insights into the instantaneous current conducted by HCN channels, showing that modifications to the region close to the intracellular gate underlie the expression of I_inst, and establishes a well-defined model for studying ¹O₂ modifications at the molecular level.

LC-MS/MS analysis and comparison of oxidative damages on peptides induced by pathogen reduction technologies for platelets

Pathogen reduction technologies (PRT) are photochemical processes that use a combination of photosensitizers and UV-light to inactivate pathogens in platelet concentrates (PCs), a blood-derived product used to prevent hemorrhage. However, different studies have questioned the impact of PRT on platelet function and transfusion efficacy, and several proteomic analyses revealed possible oxidative damages to proteins. The present work focused on the oxidative damages produced by the two main PRT on peptides. Model peptides containing residues prone to oxidation (tyrosine, histidine, tryptophane, and cysteine) were irradiated with a combination of amotosalen/UVA (Intercept process) or riboflavin/UVB (Mirasol-like process). Modifications were identified and quantified by liquid chromatography coupled to tandem mass spectrometry. Cysteine-containing peptides formed disulfide bridges (R-SS-R, -2 Da; favored following amotosalen/UVA), sulfenic and sulfonic acids (R-SOH, +16 Da, R-SO3H, +48 Da, favored following riboflavin/UVB) upon treatment and the other amino acids exhibited different oxidations revealed by mass shifts from +4 to +34 Da involving different mechanisms; no photoadducts were detected. These amino acids were not equally affected by the PRT and the combination riboflavin/UVB generated more oxidation than amotosalen/UVA. This work identifies the different types and sites of peptide oxidations under the photochemical treatments and demonstrates that the two PRT may behave differently. The potential impact on proteins and platelet functions may thus be PRT-dependent.

Reactive oxygen species: re-evaluation of generation, monitoring and role in stress-signaling in phototrophic organisms

This review provides an overview about recent developments and current knowledge about monitoring, generation and the functional role of reactive oxygen species (ROS) - H2O2, HO2, HO, OH(-), (1)O2 and O2(-) - in both oxidative degradation and signal transduction in photosynthetic organisms including microscopic techniques for ROS detection and controlled generation. Reaction schemes elucidating formation, decay and signaling of ROS in cyanobacteria as well as from chloroplasts to the nuclear genome in eukaryotes during exposure of oxygen-evolving photosynthetic organisms to oxidative stress are discussed that target the rapidly growing field of regulatory effects of ROS on nuclear gene expression.

Lipid Peroxidation: Production, Metabolism, and Signaling Mechanisms of Malondialdehyde and 4-Hydroxy-2-Nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970–1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010–2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews ofin vivomammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid Peroxidation: Production, Metabolism, and Signaling Mechanisms of Malondialdehyde and 4-Hydroxy-2-Nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970–1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010–2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews ofin vivomammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid Peroxidation: Production, Metabolism, and Signaling Mechanisms of Malondialdehyde and 4-Hydroxy-2-Nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970–1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010–2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews ofin vivomammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid Peroxidation: Production, Metabolism, and Signaling Mechanisms of Malondialdehyde and 4-Hydroxy-2-Nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970–1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010–2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews ofin vivomammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid Peroxidation: Production, Metabolism, and Signaling Mechanisms of Malondialdehyde and 4-Hydroxy-2-Nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970–1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010–2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews ofin vivomammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid Peroxidation: Production, Metabolism, and Signaling Mechanisms of Malondialdehyde and 4-Hydroxy-2-Nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970–1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010–2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews ofin vivomammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Lipid Peroxidation: Production, Metabolism, and Signaling Mechanisms of Malondialdehyde and 4-Hydroxy-2-Nonenal

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970–1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010–2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews ofin vivomammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.