New insights regarding the autoxidation of polyunsaturated fatty acids

Complexing Protein-Free Botulinum Neurotoxin A Formulations: Implications of Excipients for Immunogenicity

The formation of neutralizing antibodies is a growing concern in the use of botulinum neurotoxin A (BoNT/A) as it may result in secondary treatment failure. Differences in the immunogenicity of BoNT/A formulations have been attributed to the presence of pharmacologically unnecessary bacterial components. Reportedly, the rate of antibody-mediated secondary non-response is lowest in complexing protein-free (CF) IncobotulinumtoxinA (INCO). Here, the published data and literature on the composition and properties of the three commercially available CF-BoNT/A formulations, namely, INCO, Coretox® (CORE), and DaxibotulinumtoxinA (DAXI), are reviewed to elucidate the implications for their potential immunogenicity. While all three BoNT/A formulations are free of complexing proteins and contain the core BoNT/A molecule as the active pharmaceutical ingredient, they differ in their production protocols and excipients, which may affect their immunogenicity. INCO contains only two immunologically inconspicuous excipients, namely, human serum albumin and sucrose, and has demonstrated low immunogenicity in daily practice and clinical studies for more than ten years. DAXI contains four excipients, namely, L-histidine, trehalosedihydrate, polysorbate 20, and the highly charged RTP004 peptide, of which the latter two may increase the immunogenicity of BoNT/A by introducing neo-epitopes. In early clinical studies with DAXI, antibodies against BoNT/A and RTP004 were found at low frequencies; however, the follow-up period was critically short, with a maximum of three injections. CORE contains four excipients: L-methionine, sucrose, NaCl, and polysorbate 20. Presently, no data are available on the immunogenicity of CORE in human beings. It remains to be seen whether all three CF BoNT/A formulations demonstrate the same low immunogenicity in patients over a long period of time.

Endogenous Photosensitizers in Human Skin

Endogenous photosensitizers play a critical role in both beneficial and harmful light-induced transformations in biological systems. Understanding their mode of action is essential for advancing fields such as photomedicine, photoredox catalysis, environmental science, and the development of sun care products. This review offers a comprehensive analysis of endogenous photosensitizers in human skin, investigating the connections between their electronic excitation and the subsequent activation or damage of organic biomolecules. We gather the physicochemical and photochemical properties of key endogenous photosensitizers and examine the relationships between their chemical reactivity, location within the skin, and the primary biochemical events following solar radiation exposure, along with their influence on skin physiology and pathology. An important take-home message of this review is that photosensitization allows visible light and UV-A radiation to have large effects on skin. The analysis presented here unveils potential causes for the continuous increase in global skin cancer cases and emphasizes the limitations of current sun protection approaches.

Redox phospholipidomics discovers pro-ferroptotic death signals in A375 melanoma cells in vitro and in vivo

Growing cancer cells effectively evade most programs of regulated cell death, particularly apoptosis. This necessitates a search for alternative therapeutic modalities to cause cancer cell's demise, among them - ferroptosis. One of the obstacles to using pro-ferroptotic agents to treat cancer is the lack of adequate biomarkers of ferroptosis. Ferroptosis is accompanied by peroxidation of polyunsaturated species of phosphatidylethanolamine (PE) to hydroperoxy- (-OOH) derivatives, which act as death signals. We demonstrate that RSL3-induced death of A375 melanoma cells in vitro was fully preventable by ferrostatin-1, suggesting their high susceptibility to ferroptosis. Treatment of A375 cells with RSL3 caused a significant accumulation of PE-(18:0/20:4-OOH) and PE-(18:0/22:4-OOH), the biomarkers of ferroptosis, as well as oxidatively truncated products - PE-(18:0/hydroxy-8-oxo-oct-6-enoic acid (HOOA) and PC-(18:0/HOOA). A significant suppressive effect of RSL3 on melanoma growth was observed in vivo (utilizing a xenograft model of inoculation of GFP-labeled A375 cells into immune-deficient athymic nude mice). Redox phospholipidomics revealed elevated levels of 18:0/20:4-OOH in RSL3-treated group vs controls. In addition, PE-(18:0/20:4-OOH) species were identified as major contributors to the separation of control and RSL3-treated groups, with the highest variable importance in projection predictive score. Pearson correlation analysis revealed an association between tumor weight and contents of PE-(18:0/20:4-OOH) (r = -0.505), PE-18:0/HOOA (r = -0.547) and PE 16:0-HOOA (r = -0.503). Thus, LC-MS/MS based redox lipidomics is a sensitive and precise approach for the detection and characterization of phospholipid biomarkers of ferroptosis induced in cancer cells by radio- and chemotherapy.

Colorimetric Sensing of the Peroxide Number of Milk Powder Using CsPbBr3 Perovskite Nanocrystals

In this study, a wavelength-shift-based colorimetric sensing approach for the peroxide number of milk powder using CsPbBr₃ perovskite nanocrystals (CsPbBr₃ NCs) has been developed. Through the fat extraction, REDOX reactions and halogen exchange, as well as the optimized experimental conditions, a colorimetric sensing method was established to determine the peroxide number of milk powder samples. The integrated process of milk powder fat extraction and the REDOX process greatly shortened the determination time. This colorimetric method has a good linear correlation in the range of the peroxide number from 0.02 to 1.96 mmol/kg, and the detection limit was found to be 3 μmol/kg. This study further deepens the application prospect of wavelength-shift-based colorimetric sensing using CsPbBr₃ NCs.

Diet as a Source of Acrolein: Molecular Basis of Aldehyde Biological Activity in Diabetes and Digestive System Diseases

Acrolein, a highly reactive α,β-unsaturated aldehyde, is a compound involved in the pathogenesis of many diseases, including neurodegenerative diseases, cardiovascular and respiratory diseases, diabetes mellitus, and the development of cancers of various origins. In addition to environmental pollution (e.g., from car exhaust fumes) and tobacco smoke, a serious source of acrolein is our daily diet and improper thermal processing of animal and vegetable fats, carbohydrates, and amino acids. Dietary intake is one of the main routes of human exposure to acrolein, which is a major public health concern. This review focuses on the molecular mechanisms of acrolein activity in the context of its involvement in the pathogenesis of diseases related to the digestive system, including diabetes, alcoholic liver disease, and intestinal cancer.

Recent innovations and emerging technological advances used to improve quality and process of plant-based milk analogs

The worldwide challenges related to food sustainability are presently more critical than ever before due to the severe consequences of climate change, outbreak of epidemics, and wars. Many consumers are shifting their dietary habits toward consuming more plant-based foods, such as plant milk analogs (PMA) for health, sustainability, and well-being reasons. The PMA market is anticipated to reach US$38 billion within 2024, making them the largest segment in plant-based foods. Nevertheless, using plant matrices to produce PMA has numerous limitations, including, among others, low stability and short shelf life. This review addresses the main obstacles facing quality and safety of PMA formula. Moreover, this literature overview discusses the emerging approaches, e.g., pulsed electric field (PEF), cold atmospheric plasma (CAP), ultrasound (US), ultra-high-pressure homogenization (UHPH), ultraviolet C (UVC) irradiation, ozone (O3), and hurdle technology used in PMA formulations to overcome their common challenges. These emerging technologies have a vast potential at the lab scale to improve physicochemical characteristics, increase stability and extend the shelf-life, decrease food additives, increase nutritional and organoleptic qualities of the end product. Although the PMA fabrication on a large scale using these technologies can be expected in the near future to formulate novel food products that can offer green alternatives to conventional dairy products, further development is still needed for wider commercial applications.

Viridiplantae-specific GLXI and GLXII isoforms co-evolved and detoxify glucosone in planta

Reactive carbonyl species (RCS) such as methylglyoxal (MGO) and glyoxal (GO) are highly reactive, unwanted side-products of cellular metabolism maintained at harmless intracellular levels by specific scavenging mechanisms.MGO and GO are metabolized through the glyoxalase (GLX) system, which consists of two enzymes acting in sequence, GLXI and GLXII. While plant genomes encode a number of different GLX isoforms, their specific functions and how they arose during evolution are unclear. Here, we used Arabidopsis (Arabidopsis thaliana) as a model species to investigate the evolutionary history of GLXI and GLXII in plants and whether the GLX system can protect plant cells from the toxicity of RCS other than MGO and GO. We show that plants possess two GLX systems of different evolutionary origins and with distinct structural and functional properties. The first system is shared by all eukaryotes, scavenges MGO and GO, especially during seedling establishment, and features Zn2+-type GLXI proteins with a metal cofactor preference that were present in the last eukaryotic common ancestor. GLXI and GLXII of the second system, featuring Ni2+-type GLXI, were acquired by the last common ancestor of Viridiplantae through horizontal gene transfer from proteobacteria and can together metabolize keto-D-glucose (KDG, glucosone), a glucose-derived RCS, to D-gluconate. When plants displaying loss-of-function of a Viridiplantae-specific GLXI were grown in KDG, D-gluconate levels were reduced to 10%-15% of those in the wild type, while KDG levels showed an increase of 48%-67%. In contrast to bacterial GLXI homologs, which are active as dimers, plant Ni2+-type GLXI proteins contain a domain duplication, are active as monomers, and have a modified second active site. The acquisition and neofunctionalization of a structurally, biochemically, and functionally distinct GLX system indicates that Viridiplantae are under strong selection to detoxify diverse RCS.

Biological autoluminescence as a perturbance-free method for monitoring oxidation in biosystems

Biological oxidation processes are in the core of life energetics, play an important role in cellular biophysics, physiological cell signaling or cellular pathophysiology. Understanding of biooxidation processes is also crucial for biotechnological applications. Therefore, a plethora of methods has been developed for monitoring oxidation so far, each with distinct advantages and disadvantages. We review here the available methods for monitoring oxidation and their basic characteristics and capabilities. Then we focus on a unique method - the only one that does not require input of additional external energy or chemicals - which employs detection of biological autoluminescence (BAL). We highlight the pros and cons of this method and provide an overview of how BAL can be used to report on various aspects of cellular oxidation processes starting from oxygen consumption to the generation of oxidation products such as carbonyls. This review highlights the application potential of this completely non-invasive and label-free biophotonic diagnostic method.

Poloxamer 188 as surfactant in biological formulations - An alternative for polysorbate 20/80?

Surfactants are used to stabilize biologics. Particularly, polysorbates (Tween® 20 and Tween® 80) dominate the group of surfactants in protein and especially antibody drug products. Since decades drug developers rely on the ethoxylated sorbitan fatty acid ester mixtures to stabilize sensitive molecules such as proteins. Reasons are (i) excellent stabilizing properties, and (ii) well recognized safety and tolerability profile of these polysorbates in humans, especially for parenteral applications. However, over the past decade concerns regarding the stability of these two polysorbates were raised. The search of alternatives with preferably less reservations concerning degradation and product quality reducing issues leads, among others, to poloxamer 188 (e.g. Kolliphor® P188), a nonionic triblock-copolymer surfactant. This review sums up our current knowledge related to the characterization and physico-chemical properties of poloxamer 188, its analytics and stability properties for biological formulations. Furthermore, the advantages and disadvantages as a suitable polysorbate-alternative for the stabilization of biologics are discussed.

In-situ synthesis of metal nanoparticle embedded soft hybrid materials via eco-benign approach

The unique optical and electronic properties of metal nanoparticles and tunable properties of the organic templates encourage the scientific community to generate metal nanoparticle embedded soft hybrid materials for various novel utilities. Here, we discuss the in-situ synthesis of metal nanoparticle embedded soft hybrid materials via eco-benign approach which exclude the use of toxic reducing/capping agents or toxic reaction media. In this protocol, the gel matrix composed of benign organic templates act as reducing as well as stabilizing agent for the in-situ generation and stabilization of metal nanoparticles. As the incorporation of metal salts (as nanoparticle precursor) in the gel medium is required in this process, in most of the cases aqueous media were used for the generation of metal nanoparticle embedded soft hybrid materials. This discussion includes interesting findings from our laboratory where hybrid gel matrix composed of renewable chemicals was utilized for the in-situ synthesis of palladium nanoparticle embedded soft trihybrid material. The hybrid gel matrix rich in polyphenols/flavonoids was exploited to generate palladium nanoparticle embedded trihybrid gel through in-situ reduction of doped Pd (II) salts to stable PdNPs. The xerogel of this trihybrid material was utilized as recyclable heterogeneous catalyst for C-C coupling reaction in air under phosphene free condition and reduction reaction.

Inflammatory Cells in Atherosclerosis

Atherosclerosis is a chronic progressive disease that involves damage to the intima, inflammatory cell recruitment and the accumulation of lipids followed by calcification and plaque rupture. Inflammation is considered a key mediator of many events during the development and progression of the disease. Various types of inflammatory cells are reported to be involved in atherosclerosis. In the present paper, we discuss the involved inflammatory cells, their characteristic and functional significance in the development and progression of atherosclerosis. The detailed understanding of the role of all these cells in disease progression at different stages sheds more light on the subject and provides valuable insights as to where and when therapy should be targeted.

Fatty acid dioxygenase-cytochrome P450 fusion enzymes of filamentous fungal pathogens

Oxylipins designate oxygenated unsaturated C₁₈ fatty acids. Many filamentous fungi pathogens contain dioxygenases (DOX) in oxylipin biosynthesis with homology to human cyclooxygenases. They contain a DOX domain, which is often fused to a functional cytochrome P450 at the C-terminal end. A Tyr radical in the DOX domain initiates dioxygenation of linoleic acid by hydrogen abstraction with formation of 8-, 9-, or 10-hydroperoxy metabolites. The P450 domains can catalyze heterolytic cleavage of 8- and 10-hydroperoxides with oxidation of the heme thiolate iron for hydroxylation at C-5, C-7, C-9, or C-11 and for epoxidation of the 12Z double bond; thus displaying linoleate diol synthase (LDS) and epoxy alcohol synthase (EAS) activities. LSD activities are present in the rice blast pathogen Magnaporthe oryzae, Botrytis cinerea causing grey mold and the black scurf pathogen Rhizoctonia solani. 10R-DOX-EAS has been found in M. oryzae and Fusarium oxysporum. The P450 domains may also catalyze homolytic cleavage of 8- and 9-hydroperoxy fatty acids and dehydration to produce epoxides with an adjacent double bond, i.e., allene oxides, thus displaying 8- and 9-DOX-allene oxide synthases (AOS). F. oxysporum, F. graminearum, and R. solani express 9S-DOX-AOS and Zymoseptoria tritici 8S-and 9R-DOX-AOS. Homologues are present in endemic human-pathogenic fungi with extensive studies in Aspergillus fumigatus, A. flavus (also a plant pathogen) as well as the genetic model A. nidulans. 8R-and 10R-DOX appear to bind fatty acids "headfirst" in the active site, whereas 9S-DOX binds them "tail first" in analogy with cyclooxygenases. The biological relevance of 8R-DOX-5,8-LDS (also designated PpoA) was first discovered in relation to sporulation of A. nidulans and recently for development and programmed hyphal branching of A. fumigatus. Gene deletion DOX-AOS homologues in F. verticillioides, A. flavus, and A. nidulans alters, inter alia, mycotoxin production, sporulation, and gene expression.

Intestinal and Hepatic Uptake of Dietary Peroxidized Lipids and Their Decomposition Products, and Their Subsequent Effects on Apolipoprotein A1 and Paraoxonase1

Both pro- and antiatherosclerotic effects have been ascribed to dietary peroxidized lipids. Confusion on the role of peroxidized lipids in atherosclerotic cardiovascular disease is punctuated by a lack of understanding regarding the metabolic fate and potential physiological effects of dietary peroxidized lipids and their decomposition products. This study sought to determine the metabolic fate and physiological ramifications of 13-hydroperoxyoctadecadienoic acid (13-HPODE) and 13-HODE (13-hydroxyoctadecadienoic acid) supplementation in intestinal and hepatic cell lines, as well as any effects resulting from 13-HPODE or 13-HODE degradation products. In the presence of Caco-2 cells, 13-HPODE was rapidly reduced to 13-HODE. Upon entering the cell, 13-HODE appears to undergo decomposition, followed by esterification. Moreover, 13-HPODE undergoes autodecomposition to produce aldehydes such as 9-oxononanoic acid (9-ONA). Results indicate that 9-ONA was oxidized to azelaic acid (AzA) rapidly in cell culture media, but AzA was poorly absorbed by intestinal cells and remained detectable in cell culture media for up to 18 h. An increased apolipoprotein A1 (ApoA1) secretion was observed in Caco-2 cells in the presence of 13-HPODE, 9-ONA, and AzA, whereas such induction was not observed in HepG2 cells. However, 13-HPODE treatments suppressed paraoxonase 1 (PON1) activity, suggesting the induction of ApoA1 secretion by 13-HPODE may not represent functional high-density lipoprotein (HDL) capable of reducing oxidative stress. Alternatively, AzA induced both ApoA1 secretion and PON1 activity while suppressing ApoB secretion in differentiated Caco-2 cells but not in HepG2. These results suggest oxidation of 9-ONA to AzA might be an important phenomenon, resulting in the accumulation of potentially beneficial dietary peroxidized lipid-derived aldehydes.

WITHDRAWN: Fatty acid dioxygenase-cytochrome P450 fusion enzymes of the top 10 fungal pathogens in molecular plant pathology and human-pathogenic fungi

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Effects of Inclusion of Schizochytrium spp. and Forage-to-Concentrate Ratios on Goats' Milk Quality and Oxidative Status

Although the dietary inclusion level of polyunsaturated fatty acids (PUFA) and the forage: concentrate (F:C) ratio affect milk quality, their interaction has not been broadly studied. To address such gaps and limitations a two-phase trial using twenty-two dairy goats was carried out. During the first phase, both groups (20 HF n = 11; high forage and 20 HG n = 11; high grain) were supplemented with 20 g Schizochytrium spp./goat/day. The 20 HF group consumed a diet with F:C ratio 60:40 and the 20 HG-diet consisted of F:C = 40:60. In the second phase, the supplementation level of Schizochytrium spp. was increased to 40 g/day/goat while the F:C ratio between the two groups were remained identical (40 HF n = 11; high forage and 40 HG n = 11; high grain). Neither the Schizochytrium spp. supplementation levels (20 vs. 40) nor the F:C ratio (60:40 vs. 40:60) affected milk performance. The high microalgae level (40 g) in combination with high grain diet (40 HG) modified the proportions of docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), and conjugated linoleic acid (CLA) and the ω3/ω6 ratio in milk, to a beneficial manner according to human health recommendation guidelines. However, the highest inclusion level of Schizochytrium spp. (40 g) and foremost in combination with the high grain diets (40 HG) induced an oxidative response as observed by the increased protein carbonyls (CP) and malondialdehyde (MDA) levels in milk and blood plasma indicating severe limitations for a long-term, on-farm application. In conclusion, the supplementation with 20 g Schizochytrium spp. and high forage diet (60:40) appears to be an ideal formula to enrich dairy products with essential biomolecules for human health without adversely affect milk oxidative stability.

Ferroptosis and cardiovascular disease: role of free radical-induced lipid peroxidation

Cardiovascular disease (CVD), including heart attack, stroke, heart failure, arrhythmia, and other congenital heart diseases remain the leading cause of morbidity and mortality worldwide. The leading cause of deaths in CVD is attributed to myocardial infarction due to the rupture of atherosclerotic plaque. Atherosclerosis refers a condition when restricted or even blockage of blood flow occurs due to the narrowing of blood vessels as a result of the buildup of plaques composed of oxidized lipids. It is well-established that free radical oxidation of polyunsaturated fatty acids (PUFAs) in lipoproteins or cell membranes, termed lipid peroxidation (LPO), plays a significant role in atherosclerosis. LPO products are involved in immune responses and cell deaths in this process, in which previous evidence supports the role of programmed cell death (apoptosis) and necrosis. Ferroptosis is a newly identified form of regulated cell death characterized by the iron-dependent accumulation of lipid hydroperoxides to lethal levels, which exhibits distinct features from apoptosis, necrosis and autophagy in morphology, biochemistry and genetics. Emerging evidence appears to demonstrate that ferroptosis is also involved in CVD. In this review, we summarize the recent progress on ferroptosis in CVD and atherosclerosis, highlighting the role of free radical LPO. The evidence underlying the ferroptosis and challenges in the field will also be critically discussed.

Targeting Lipid Peroxidation for Cancer Treatment

Cancer is one of the highest prevalent diseases in humans. The chances of surviving cancer and its prognosis are very dependent on the affected tissue, body location, and stage at which the disease is diagnosed. Researchers and pharmaceutical companies worldwide are pursuing many attempts to look for compounds to treat this malignancy. Most of the current strategies to fight cancer implicate the use of compounds acting on DNA damage checkpoints, non-receptor tyrosine kinases activities, regulators of the hedgehog signaling pathways, and metabolic adaptations placed in cancer. In the last decade, the finding of a lipid peroxidation increase linked to 15-lipoxygenases isoform 1 (15-LOX-1) activity stimulation has been found in specific successful treatments against cancer. This discovery contrasts with the production of other lipid oxidation signatures generated by stimulation of other lipoxygenases such as 5-LOX and 12-LOX, and cyclooxygenase (COX-2) activities, which have been suggested as cancer biomarkers and which inhibitors present anti-tumoral and antiproliferative activities. These findings support the previously proposed role of lipid hydroperoxides and their metabolites as cancer cell mediators. Depletion or promotion of lipid peroxidation is generally related to a specific production source associated with a cancer stage or tissue in which cancer originates. This review highlights the potential therapeutical use of chemical derivatives to stimulate or block specific cellular routes to generate lipid hydroperoxides to treat this disease.

Identification of acrolein as the reactive carbonyl responsible for the formation of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx)

Reaction mixtures of reactive carbonyls and creatinine were submitted to high temperature and studied to identify the reactive carbonyl(s) responsible for 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) formation. MeIQx was produced by reaction of acrolein and creatinine within a wide pH range and with an activation energy of 81.1 ± 1.4 kJ/mol. No additional reactants were required, although methylglyoxal, ammonia, and formaldehyde also participated in the reaction. Nevertheless, these additional reactants were produced in situ from either acrolein or creatinine. A reaction pathway that both explains the formation of MeIQx and is valid for the formation of other heterocyclic aromatic amines (HAAs) with the structure of quinoxaline is proposed. Obtained results demonstrate the key role of reactive carbonyls present in foods (the food carbonylome) on HAA formation. Because creatinine is ubiquitous in proteinaceous foods, the control of the food carbonylome seems to be the key point to control HAA formation in foods.

Protein Formulations Containing Polysorbates: Are Metal Chelators Needed at All?

Proteins are prone to post-translational modifications at specific sites, which can affect their physicochemical properties, and consequently also their safety and efficacy. Sources of post-translational modifications include oxygen and reactive oxygen species. Additionally, catalytic amounts of Fe(II) or Cu(I) can promote increased activities of reactive oxygen species, and thus catalyse the production of particularly reactive hydroxyl radicals. When oxidative post-translational modifications are detected in the biopharmaceutical industry, it is common practice to add chelators to the formulation. However, the resultant complexes with metals can be even more damaging. Indeed, this is supported here using an ascorbate redox system assay and peptide mapping. Ethylenediaminetetraacetic acid (EDTA) addition strongly accelerated the formation of hydroxyl radicals in an iron-ascorbate system, while diethylenetriaminepentaacetic acid (DTPA) addition did not. When Fe(III) was substituted with Cu(II), EDTA addition almost stopped hydroxyl radical production, whereas DTPA addition showed continued production, but at a reduced rate. Further, EDTA accelerated metal-catalysed oxidation of proteins, and thus did not protect them from Fe-mediated oxidative damage. As every formulation is unique, justification for EDTA or DTPA addition should be based on experimental data and not common practice.

Inhibition of lipid peroxidation during the reproductive period extends the lifespan of Caenorhabditis elegans

Glutathione peroxidase 4 (GPx4) is a unique antioxidant enzyme that directly reduces the phospholipid hydroperoxides (PLOOH) generated in biomembranes using glutathione as the reductant. We have previously reported that the Caenorhabditis elegans gpx-quad mutant, which lacks all homologous genes of GPx4 has a reduced lifespan compared with the wild-type. However, the mechanisms underlying the lifespan reduction remain unclear. By monitoring the change in PLOOH production with age, we found that PLOOH was elevated in the gpx-quad mutants compared with the wild-type during the reproductive period. Administration of vitamin E not only reduced the PLOOH content but also prolonged the lifespan of the gpx-quad mutants. In contrast, vitamin C did not extend the lifespan of the gpx-quad mutants. Interestingly, we found that the inhibition of lipid peroxidation by vitamin E during 5 to 10 days after hatching is important to extend the lifespan of C. elegans. These results suggest that production of PLOOH during the reproductive period strongly influences the lifespan of C. elegans.

Detection, identification, and quantification of oxidative protein modifications

Exposure of biological molecules to oxidants is inevitable and therefore commonplace. Oxidative stress in cells arises from both external agents and endogenous processes that generate reactive species, either purposely (e.g. during pathogen killing or enzymatic reactions) or accidentally (e.g. exposure to radiation, pollutants, drugs, or chemicals). As proteins are highly abundant and react rapidly with many oxidants, they are highly susceptible to, and major targets of, oxidative damage. This can result in changes to protein structure, function, and turnover and to loss or (occasional) gain of activity. Accumulation of oxidatively-modified proteins, due to either increased generation or decreased removal, has been associated with both aging and multiple diseases. Different oxidants generate a broad, and sometimes characteristic, spectrum of post-translational modifications. The kinetics (rates) of damage formation also vary dramatically. There is a pressing need for reliable and robust methods that can detect, identify, and quantify the products formed on amino acids, peptides, and proteins, especially in complex systems. This review summarizes several advances in our understanding of this complex chemistry and highlights methods that are available to detect oxidative modifications-at the amino acid, peptide, or protein level-and their nature, quantity, and position within a peptide sequence. Although considerable progress has been made in the development and application of new techniques, it is clear that further development is required to fully assess the relative importance of protein oxidation and to determine whether an oxidation is a cause, or merely a consequence, of injurious processes.

Drugs Repurposed as Antiferroptosis Agents Suppress Organ Damage, Including AKI, by Functioning as Lipid Peroxyl Radical Scavengers

BACKGROUND

Ferroptosis, nonapoptotic cell death mediated by free radical reactions and driven by the oxidative degradation of lipids, is a therapeutic target because of its role in organ damage, including AKI. Ferroptosis-causing radicals that are targeted by ferroptosis suppressors have not been unequivocally identified. Because certain cytochrome P450 substrate drugs can prevent lipid peroxidation via obscure mechanisms, we evaluated their antiferroptotic potential and used them to identify ferroptosis-causing radicals.

METHODS

Using a cell-based assay, we screened cytochrome P450 substrate compounds to identify drugs with antiferroptotic activity and investigated the underlying mechanism. To evaluate radical-scavenging activity, we used electron paramagnetic resonance-spin trapping methods and a fluorescence probe for lipid radicals, NBD-Pen, that we had developed. We then assessed the therapeutic potency of these drugs in mouse models of cisplatin-induced AKI and LPS/galactosamine-induced liver injury.

RESULTS

We identified various US Food and Drug Administration-approved drugs and hormones that have antiferroptotic properties, including rifampicin, promethazine, omeprazole, indole-3-carbinol, carvedilol, propranolol, estradiol, and thyroid hormones. The antiferroptotic drug effects were closely associated with the scavenging of lipid peroxyl radicals but not significantly related to interactions with other radicals. The elevated lipid peroxyl radical levels were associated with ferroptosis onset, and known ferroptosis suppressors, such as ferrostatin-1, also functioned as lipid peroxyl radical scavengers. The drugs exerted antiferroptotic activities in various cell types, including tubules, podocytes, and renal fibroblasts. Moreover, in mice, the drugs ameliorated AKI and liver injury, with suppression of tissue lipid peroxidation and decreased cell death.

CONCLUSIONS

Although elevated lipid peroxyl radical levels can trigger ferroptosis onset, some drugs that scavenge lipid peroxyl radicals can help control ferroptosis-related disorders, including AKI.

Recent development on liquid chromatography-mass spectrometry analysis of oxidized lipids

Polyunsaturated fatty acids (PUFAs) in the cellular membrane can be oxidized by various enzymes or reactive oxygen species (ROS) to form many oxidized lipids. These metabolites are highly bioactive, participating in a variety of physiological and pathophysiological processes. Mass spectrometry (MS), coupled with Liquid Chromatography, has been increasingly recognized as an indispensable tool for the analysis of oxidized lipids due to its excellent sensitivity and selectivity. We will give an update on the understanding of the molecular mechanisms related to generation of various oxidized lipids and recent progress on the development of LC-MS in the detection of these bioactive lipids derived from fatty acids, cholesterol esters, and phospholipids. The purpose of this review is to provide an overview of the formation mechanisms and technological advances in LC-MS for the study of oxidized lipids in human diseases, and to shed new light on the potential of using oxidized lipids as biomarkers and mechanistic clues of pathogenesis related to lipid metabolism. The key technical problems associated with analysis of oxidized lipids and challenges in the field will also discussed.

An update on lipid oxidation and inflammation in cardiovascular diseases

Cardiovascular diseases (CVD), including ischemic heart diseases and cerebrovascular diseases, are the leading causes of morbidity and mortality worldwide. Atherosclerosis is the major underlying factor for most CVD. It is well-established that oxidative stress and inflammation are two major mechanisms leading to atherosclerosis. Under oxidative stress, polyunsaturated fatty acids (PUFA)-containing phospholipids and cholesterol esters in cellular membrane and lipoproteins can be readily oxidized through a free radical-induced lipid peroxidation (LPO) process to form a complex mixture of oxidation products. Overwhelming evidence demonstrates that these oxidized lipids are actively involved in the inflammatory responses in atherosclerosis by interacting with immune cells (such as macrophages) and endothelial cells. In addition to lipid lowering in the prevention and treatment of atherosclerotic CVD, targeting chronic inflammation has been entering the medical realm. Clinical trials are under way to lower the lipoprotein (a) (Lp(a)) and its associated oxidized phospholipids, which will provide clinical evidence that targeting inflammation caused by oxidized lipids is a viable approach for CVD. In this review, we aim to give an update on our understanding of the free radical oxidation of LPO, analytical technique to analyze the oxidation products, especially the oxidized phospholipids and cholesterol esters in low density lipoproteins (LDL), and focusing on the experimental and clinical evidence on the role of lipid oxidation in the inflammatory responses associated with CVD, including myocardial infarction and calcific aortic valve stenosis. The challenges and future directions in understanding the role of LPO in CVD will also be discussed.

Mass Spectrometry Characterization of Thiol Conjugates Linked to Polyoxygenated Polyunsaturated Fatty Acid Species

Radical mediated oxidation of polyunsaturated fatty acids (PUFA) is known to generate a series of polyoxygenated cyclic products (PUFA-O_n, n ≥ 3). Here, we describe the characterization of glutathione (GSH) conjugates bound to polyoxygenated docosahexaenoic (DHA-O_n, n = 3-9), arachidonic (ARA-O_n, n = 3-7), α-linolenic (ALA-O₃), and linoleic (LA-O₃) acid species. Similar conjugates were also characterized for N-acetylcysteine (NAC) and Cu,Zn-superoxide dismutase (SOD1). Extensive LC-MS/MS characterization using a synthetic α-linolenic hydroxy-endoperoxide (ALA-O₃) derivative revealed at least two types of mechanisms leading to thiol adduction: a mechanism involving the nucleophilic attack by thiolate anion on 1,2-dioxolane to form a sulfenate ester-bonded conjugate and a mechanism involving cleavage of the dioxolane to form a α,β-unsaturated carbonyl followed by the Michael addition reaction. Finally, we detected a GSH conjugate with hydroxy-endoperoxide derived from linoleic acid (LA-O₃) in mice liver. In summary, our study reveals the formation of a series of thiol conjugates that are bound to highly oxygenated PUFA species. GSH conjugates described in our study may potentially play relevant roles in redox and inflammatory processes, especially under high oxygen tension conditions.

Post-Translational Modification of Proteins Mediated by Nitro-Fatty Acids in Plants: Nitroalkylation

Nitrate fatty acids (NO₂-FAs) are considered reactive lipid species derived from the non-enzymatic oxidation of polyunsaturated fatty acids by nitric oxide (NO) and related species. Nitrate fatty acids are powerful biological electrophiles which can react with biological nucleophiles such as glutathione and certain protein⁻amino acid residues. The adduction of NO₂-FAs to protein targets generates a reversible post-translational modification called nitroalkylation. In different animal and human systems, NO₂-FAs, such as nitro-oleic acid (NO₂-OA) and conjugated nitro-linoleic acid (NO₂-cLA), have cytoprotective and anti-inflammatory influences in a broad spectrum of pathologies by modulating various intracellular pathways. However, little knowledge on these molecules in the plant kingdom exists. The presence of NO₂-OA and NO₂-cLA in olives and extra-virgin olive oil and nitro-linolenic acid (NO₂-Ln) in Arabidopsis thaliana has recently been detected. Specifically, NO₂-Ln acts as a signaling molecule during seed and plant progression and beneath abiotic stress events. It can also release NO and modulate the expression of genes associated with antioxidant responses. Nevertheless, the repercussions of nitroalkylation on plant proteins are still poorly known. In this review, we demonstrate the existence of endogenous nitroalkylation and its effect on the in vitro activity of the antioxidant protein ascorbate peroxidase.

Lipoxidation in cardiovascular diseases

Lipids can go through lipid peroxidation, an endogenous chain reaction that consists in the oxidative degradation of lipids leading to the generation of a wide variety of highly reactive carbonyl species (RCS), such as short-chain carbonyl derivatives and oxidized truncated phospholipids. RCS exert a wide range of biological effects due to their ability to interact and covalently bind to nucleophilic groups on other macromolecules, such as nucleic acids, phospholipids, and proteins, forming reversible and/or irreversible modifications and generating the so-called advanced lipoxidation end-products (ALEs). Lipoxidation plays a relevant role in the onset of cardiovascular diseases (CVD), mainly in the atherosclerosis-based diseases in which oxidized lipids and their adducts have been extensively characterized and associated with several processes responsible for the onset and development of atherosclerosis, such as endothelial dysfunction and inflammation. Herein we will review the current knowledge on the sources of lipids that undergo oxidation in the context of cardiovascular diseases, both from the bloodstream and tissues, and the methods for detection, characterization, and quantitation of their oxidative products and protein adducts. Moreover, lipoxidation and ALEs have been associated with many oxidative-based diseases, including CVD, not only as potential biomarkers but also as therapeutic targets. Indeed, several therapeutic strategies, acting at different levels of the ALEs cascade, have been proposed, essentially blocking ALEs formation, but also their catabolism or the resulting biological responses they induce. However, a deeper understanding of the mechanisms of formation and targets of ALEs could expand the available therapeutic strategies.

Time-Dependent ATR-FTIR Spectroscopic Studies on Solvent Diffusion and Film Swelling in Oil Paint Model Systems

In the restoration of paintings, solvent diffusion and swelling of polymeric oil paint binding media are important factors to consider. Common cleaning methods with organic solvents or aqueous solutions could lead to undesirable physicochemical changes in the paint in the long term, though the extent of this effect is not yet clear. We used tailored nonporous model systems for aged oil paint to measure paint swelling and solvent diffusion for a wide range of relevant solvents. Using dynamic mechanical analysis (DMA), the glass transition temperature of our model systems was found to be close to room temperature. Subsequently, with a custom sample cell and time-dependent attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, we were able to accurately track swelling and diffusion processes in the polymer films. To quantify the spectroscopic data, we developed a model that completely describes the solvent migration process, including significant film swelling and non-Fickian solvent diffusion. The relation between solvent properties, the diffusion coefficient, and the swelling capacity proved to be rather complex and could not be explained using a single solvent parameter. However, it was found that strongly swelling solvents generally diffuse faster than weakly swelling solvents and that pigmentation does not significantly influence solvent diffusion. These results contribute to a better understanding of transport phenomena in paintings and support the development of improved paint restoration strategies.

The Eicosanoids, Redox-Regulated Lipid Mediators in Immunometabolic Disorders

SIGNIFICANCE

The oxidation of arachidonic acid via cyclooxygenase (COX) and lipoxygenase (LOX) activity to produce eicosanoids during inflammation is a well-known biosynthetic pathway. These lipid mediators are involved in fever, pain, and thrombosis and are produced from multiple cells as well as cell/cell interactions, for example, immune cells and epithelial/endothelial cells. Metabolic disorders, including hyperlipidemia, hypertension, and diabetes, are linked with chronic low-grade inflammation, impacting the immune system and promoting a variety of chronic diseases. Recent Advances: Multiple studies have corroborated the important function of eicosanoids and their receptors in (non)-inflammatory cells in immunometabolic disorders (e.g., insulin resistance, obesity, and cardiovascular and nonalcoholic fatty liver diseases). In this context, LOX and COX products are involved in both pro- and anti-inflammatory responses. In addition, recent work has elucidated the potent function of specialized proresolving mediators (i.e., lipoxins and resolvins) in resolving inflammation, protecting organs, and stimulating tissue repair and remodeling.

CRITICAL ISSUES

Inhibiting/stimulating selected eicosanoid pathways may result in anti-inflammatory and proresolution responses leading to multiple beneficial effects, including the abrogation of reactive oxygen species production, increased speed of resolution, and overall improvement of diseases related to immunometabolic perturbations.

FUTURE DIRECTIONS

Despite many achievements, it is crucial to understand the molecular and cellular mechanisms underlying immunological/metabolic cross talk to offer substantial therapeutic promise. Antioxid. Redox Signal. 29, 275-296.

A preliminary study on the formation pathways of glycated phosphatidylethanolamine of food rich in phospholipid during the heat-processing

The formation of food-derived glycated phosphatidylethanolamine (PE) in thermal process was investigated by designing a 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE)-glucose model system heated from 40 to 100 °C for 8 h.

Abnormal pinocytosis and valence-variable behaviors of cerium suggested a cellular mechanism for plant yield reduction induced by environmental cerium

The environmental safety of cerium (Ce) applications in many fields has been debated for almost a century because the cellular effects of environmental Ce on living organisms remain largely unclear. Here, using new, interdisciplinary methods, we surprisingly found that after Ce(III) treatment, Ce(III) was first recognized and anchored on the plasma membrane in leaf cells. Moreover, some trivalent Ce(III) was oxidized to tetravalent Ce(IV) in this organelle, which activated pinocytosis. Subsequently, more anchoring sites and stronger valence-variable behavior on the plasma membrane caused stronger pinocytosis to transport Ce(III and IV) into the leaf cells. Interestingly, a great deal of Ce was bound on the pinocytotic vesicle membrane; only a small amount of Ce was enclosed in the pinocytotic vesicles. Some pinocytic vesicles in the cytoplasm were deformed and broken. Upon breaking, pinocytic vesicles released Ce into the cytoplasm, and then these Ce particles self-assembled into nanospheres. The aforementioned special behaviors of Ce decreased the fluidity of the plasma membrane, inhibited the cellular growth of leaves, and finally, decreased plant yield. In summary, our findings directly show the special cellular behavior of Ce in plant cells, which may be the cellular basis of plant yield reduction induced by environmental Ce.

Peroxyl radical- and photo-oxidation of glucose 6-phosphate dehydrogenase generates cross-links and functional changes via oxidation of tyrosine and tryptophan residues

Protein oxidation is a frequent event as a result of the high abundance of proteins in biological samples and the multiple processes that generate oxidants. The reactions that occur are complex and poorly understood, but can generate major structural and functional changes on proteins. Current data indicate that pathophysiological processes and multiple human diseases are associated with the accumulation of damaged proteins. In this study we investigated the mechanisms and consequences of exposure of the key metabolic enzyme glucose-6-phosphate dehydrogenase (G6PDH) to peroxyl radicals (ROO^•) and singlet oxygen (¹O₂), with particular emphasis on the role of Trp and Tyr residues in protein cross-linking and fragmentation. Cross-links and high molecular mass aggregates were detected by SDS-PAGE and Western blotting using specific antibodies. Amino acid analysis has provided evidence for Trp and Tyr consumption and formation of oxygenated products (diols, peroxides, N-formylkynurenine, kynurenine) from Trp, and di-tyrosine (from Tyr). Mass spectrometric data obtained after trypsin-digestion in the presence of H₂¹⁶O and H₂¹⁸O, has allowed the mapping of specific cross-linked residues and their locations. These data indicate that specific Tyr-Trp and di-Tyr cross-links are formed from residues that are proximal and surface-accessible, and that the extent of Trp oxidation varies markedly between sites. Limited modification at other residues is also detected. These data indicate that Trp and Tyr residues are readily modified by ROO^• and ¹O₂ with this giving products that impact significantly on protein structure and function. The formation of such cross-links may help rationalize the accumulation of damaged proteins in vivo.

Levels and formation of α-dicarbonyl compounds in beverages and the preventive effects of flavonoids

ABSTRACT

Methylglyoxal (MGO) and glyoxal (GO), α-dicarbonyl compounds found in the Maillard reaction, progressively and irreversibly modify proteins. Beverages are an exogenous source of α-dicarbonyl compounds and may potentially increase MGO and GO levels in vivo. Using GC-FID method, we detected the MGO and GO contents of 86 beverages in Chinese supermarkets. The highest MGO and GO 587.5 µg/100 mL and 716.7 µg/100 mL respectively found in soyamilk and coffee. Herbal beverages, which contained bioactive components, had lower average levels of MGO (48.1 µg/100 mL) and GO (25.9 µg/100 mL). A box-and-whisker plot was used to display variation of the same group drinks, and comparing distributions between six different groups. It was further discovered that fat, protein and flavonoids, in addition to sweeteners, had notable effects on the formation of MGO and GO in soybean milk. The result of LC/MS indicated that quercetin could prevent the formation of MGO by trapping MGO to form the mono-MGO and di-MGO adducts during soybean milk manufacturing.

GRAPHICAL ABSTRACT

Comprehensive metabolomics identified lipid peroxidation as a prominent feature in human plasma of patients with coronary heart diseases

Coronary heart disease (CHD) is a complex human disease associated with inflammation and oxidative stress. The underlying mechanisms and diagnostic biomarkers for the different types of CHD remain poorly defined. Metabolomics has been increasingly recognized as an enabling technique with the potential to identify key metabolomic features in an attempt to understand the pathophysiology and differentiate different stages of CHD. We performed comprehensive metabolomic analysis in human plasma from 28 human subjects with stable angina (SA), myocardial infarction (MI), and healthy control (HC). Subsequent analysis demonstrated a uniquely altered metabolic profile in these CHD: a total of 18, 37 and 36 differential metabolites were identified to distinguish SA from HC, MI from SA, and MI from HC groups respectively. Among these metabolites, glycerophospholipid (GPL) metabolism emerged as the most significantly disturbed pathway. Next, we used a targeted metabolomic approach to systematically analyze GPL, oxidized phospholipid (oxPL), and downstream metabolites derived from polyunsaturated fatty acids (PUFAs), such as arachidonic acid and linoleic acid. Surprisingly, lipids associated with lipid peroxidation (LPO) pathways including oxidized PL and isoprostanes, isomers of prostaglandins, were significantly elevated in plasma of MI patients comparing to HC and SA, consistent with the notion that oxidative stress-induced LPO is a prominent feature in CHD. Our studies using the state-of-the-art metabolomics help to understand the underlying biological mechanisms involved in the pathogenesis of CHD; LPO metabolites may serve as potential biomarkers to differentiation MI from SA and HC.

Identification of a novel series of anti-inflammatory and anti-oxidative phospholipid oxidation products containing the cyclopentenone moiety in vitro and in vivo: Implication in atherosclerosis

Oxidative stress and inflammation are two major contributing factors to atherosclerosis, a leading cause of cardiovascular disease. Oxidation of phospholipids on the surface of low density lipoprotein (LDL) particles generated under oxidative stress has been associated with the progression of atherosclerosis, but the underlying molecular mechanisms remain poorly defined. We identified a novel series of oxidation products containing the cyclopentenone moiety, termed deoxy-A₂/J₂-isoprostanes-phosphocholine, from 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine in vivo using mass spectrometry and by comparison to a chemically synthesized standard. Transcriptomic analysis (RNA-seq) demonstrated that these compounds affected >200 genes in bone marrow-derived macrophages, and genes associated with inflammatory and anti-oxidative responses are among the top 5 differentially expressed. To further investigate the biological relevance of these novel oxidized phospholipids in atherosclerosis, we chemically synthesized a representative compound 1-palmitoyl-2-15-deoxy-δ-12,14-prostaglandin J₂-sn-glycero-3-phosphocholine (15d-PGJ₂-PC) and found that it induced anti-inflammatory and anti-oxidant responses in macrophages through modulation of NF-κB, peroxisome proliferator-activated receptor γ (PPARγ), and Nrf2 pathways; this compound also showed potent anti-inflammatory properties in a mice model of LPS-induced systematic inflammatory response syndrome. Additionally, 15d-PGJ₂-PC inhibited macrophage foam cell formation, suggesting a beneficial role against atherosclerosis. These properties were consistent with decreased levels of these compounds in the plasma of patients with coronary heart disease compared with control subjects. Our findings uncovered a novel molecular mechanism for the negative regulation of inflammation and positive enhancement of anti-oxidative responses in macrophages by these oxidized phospholipids in LDL in the context of atherosclerosis.

Development of a Functional Contrast Agent for Targeting Lipid-derived Radicals

Lipid derived radicals and their metabolic products are closely involved in the pathogenesis of oxidative stress diseases, such as inflammation and angiogenesis, through the formation of a protein or DNA complex. The starting point of lipid peroxide generation is lipid-derived radicals, which increase explosively via radical chain reaction. Therefore, the trapping of lipid-derived radicals is useful in understanding the mechanism of the formation of oxidative stress diseases, and in suppressing the following chain reaction. On the other hand, nitroxides with a stable unpaired electron allow for spin trapping with carbon-centered radicals. Hence, we focused on the following points to develop lipid radical detection methods. 1) Fluorescence will be quenched through interaction with nitroxide's unpaired electron. 2) Nitroxide can react with lipid-derived radicals via radical-radical reaction. 3) Fluorescence will recover from the loss of an unpaired electron in nitroxide, after reaction with the lipid-derived radicals, by using a profluorescent nitroxide. In this paper, I will discuss the development of a lipid-derived detection method using profluorescent nitroxide switching methods, and discuss its application to cell imaging.

Impact of Cooking, Storage, and Reheating Conditions on the Formation of Cholesterol Oxidation Products in Pork Loin

This study investigates the effect of cooking, storage, and reheating conditions on the formation of cholesterol oxidation products (COPs) in pork loin. Samples of pork loin procured 24 h postmortem were initially processed and assessed for total fat and cholesterol content. The cooking methods evaluated were pan roasting, steaming, oven grilling, and microwaving. Cooked pork loin samples were stored at 4℃ and reheated after 3 and 6 d of storage using the original method of preparation or alternately, microwaving. Fat content increased significantly with cooking as a result of the loss in moisture but cholesterol content remained unchanged. Pan roasting and microwave cooking caused a significantly higher production of COPs, as with the process of reheating using microwave, pan roasting, and oven grilling methods. The major COPs found in pork loin were cholestanetriol, 20-hydroxycholesterol, and 25-hydroxycholesterol, whose concentrations varied according to the different cooking and reheating methods used. Moreover, the aerobic storage of cooked pork loin under a refrigerated condition also increased the formation of cholesterol oxides on reheating.

Clinical Relevance of Biomarkers of Oxidative Stress

SIGNIFICANCE

Oxidative stress is considered to be an important component of various diseases. A vast number of methods have been developed and used in virtually all diseases to measure the extent and nature of oxidative stress, ranging from oxidation of DNA to proteins, lipids, and free amino acids.

RECENT ADVANCES

An increased understanding of the biology behind diseases and redox biology has led to more specific and sensitive tools to measure oxidative stress markers, which are very diverse and sometimes very low in abundance.

CRITICAL ISSUES

The literature is very heterogeneous. It is often difficult to draw general conclusions on the significance of oxidative stress biomarkers, as only in a limited proportion of diseases have a range of different biomarkers been used, and different biomarkers have been used to study different diseases. In addition, biomarkers are often measured using nonspecific methods, while specific methodologies are often too sophisticated or laborious for routine clinical use.

FUTURE DIRECTIONS

Several markers of oxidative stress still represent a viable biomarker opportunity for clinical use. However, positive findings with currently used biomarkers still need to be validated in larger sample sizes and compared with current clinical standards to establish them as clinical diagnostics. It is important to realize that oxidative stress is a nuanced phenomenon that is difficult to characterize, and one biomarker is not necessarily better than others. The vast diversity in oxidative stress between diseases and conditions has to be taken into account when selecting the most appropriate biomarker.

Infant Milk Formulas: Effect of Storage Conditions on the Stability of Powdered Products towards Autoxidation

Thirty samples of powdered infant milk formulas containing polyunsaturated fatty acids (PUFAs) have been stored at four different temperatures (20, 28, 40 and 55 °C) and periodically monitored for their malondialdehyde (MDA) content up to one year. MDA levels ranged between 250 and 350 ng/kg in sealed samples with a maximum of 566 ng/kg in samples stored at 28 °C for three weeks after opening of their original packages, previously maintained for ten months at 20 °C. Sample stored at 40° and 55 °C were also submitted to CIE (Commission Internationale de l'Eclairage) colorimetric analysis, since color is the first sensorial property that consumers may evaluate. Overall, the results demonstrated a good stability of PUFA-enriched infant milk formulas in terms of MDA content. However, some care has to be paid when these products are not promptly consumed and stored for a long time after first opening.

Cooking, storage, and reheating effect on the formation of cholesterol oxidation products in processed meat products

BACKGROUND

Cholesterol is an important biological compound; however, its oxidation products have been proven to be harmful to human health. Cooking, storage, and reheating methods significantly affect the safety of meat products, as they contribute to the production of cholesterol oxidation products (COPs).

METHODS

Three cooking methods were used to cook sausages, loin ham, bacon, luncheon meat, and pressed ham, in order to investigate the effect of cooking, storage, and reheating on total cholesterol and on the formation of COPs. Cooked samples were stored at 4 °C and reheated after 3 and 6 storage days by the same cooking method or by microwaving. The samples were assessed for total lipids, cholesterol, and cholesterol oxides.

RESULTS

The average cholesterol content in the processed meat varied from 76.0 mg/100 g to 201.70 mg/100 g. Microwaved ham showed the lowest cholesterol content compared to that of other processed meat products. Significant differences were found in cholesterol content and cholesterol oxidation products depending on cooking, storage, and reheating methods. Six cholesterol oxides were found in processed meat, of which 7β-hydroxycholesterol and α-epoxides were detected as the major oxidation products.

CONCLUSIONS

Microwaving and oven grilling resulted in higher production of COPs in processed meat as compared with other cooking methods. Refrigerated storage tended to significantly increase the COPs content.

Oxidative stress in aging human skin

Oxidative stress in skin plays a major role in the aging process. This is true for intrinsic aging and even more for extrinsic aging. Although the results are quite different in dermis and epidermis, extrinsic aging is driven to a large extent by oxidative stress caused by UV irradiation. In this review the overall effects of oxidative stress are discussed as well as the sources of ROS including the mitochondrial ETC, peroxisomal and ER localized proteins, the Fenton reaction, and such enzymes as cyclooxygenases, lipoxygenases, xanthine oxidases, and NADPH oxidases. Furthermore, the defense mechanisms against oxidative stress ranging from enzymes like superoxide dismutases, catalases, peroxiredoxins, and GSH peroxidases to organic compounds such as L-ascorbate, α-tocopherol, beta-carotene, uric acid, CoQ10, and glutathione are described in more detail. In addition the oxidative stress induced modifications caused to proteins, lipids and DNA are discussed. Finally age-related changes of the skin are also a topic of this review. They include a disruption of the epidermal calcium gradient in old skin with an accompanying change in the composition of the cornified envelope. This modified cornified envelope also leads to an altered anti-oxidative capacity and a reduced barrier function of the epidermis.

Singlet-oxygen-derived products from linoleate activate Nrf2 signaling in skin cells

Linoleates are required for normal mammalian health and development, but they are also prone to oxidation, resulting in biologically active metabolites such as hydroxyoctadecadienoic acids (HODEs). To investigate the biological activity of 9-EZ-HODE, 10-EZ-HODE, 12-ZE-HODE, and 13-ZE-HODE, the metabolites of singlet-oxygen-derived products from linoleates, we assessed adaptive cytoprotection in HaCaT skin cells. Treating HaCaT cells with sublethal concentrations of 10-EZ-HODE and 12-ZE-HODE, which are singlet-oxygen-mediated specific oxidation metabolites of linoleates, but not 9-EZ-HODE and 13-ZE-HODE, caused resistance to hydrogen peroxide-induced oxidative damage. Microarray analysis of HaCaT cells revealed that 10-EZ-HODE and 12-ZE-HODE induced cellular antioxidant genes that are responsive to nuclear factor-erythroid 2 p45-related factor 2 (Nrf2), such as heme oxygenase-1 and glutathione synthesis enzymes. Although 10-EZ-HODE and 12-ZE-HODE did not induce Nrf2 mRNA, treatment with these metabolites increased the intranuclear expression of Nrf2. These results suggest that 10-EZ-HODE and 12-ZE-HODE initiate adaptive responses that reduce the damage caused by oxidative stress.

Kinetics and thermodynamics of 1-hydroxyethyl radical reaction with unsaturated lipids and prenylflavonoids

Hydroxyalkyl radicals have been reported to induce lipid oxidation as the key aspect of the pathogenesis of alcoholic fatty liver disease and are responsible for the alkylation and cleavage of DNA during the metabolism of a wide range of genotoxic compounds. However, relevant kinetic data for the oxidation of unsaturated lipids by 1-hydroxyethyl radical (HER) has not been reported. In this study, the rate constants for the reaction of unsaturated fatty acid methyl esters and sterols with HER have been determined using a competitive kinetic approach employing the spin-trap α-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) as the competitive substrate. Polyunsaturated fatty acid methyl ester is shown to react with HER with an apparent second-order rate constant ranging from (3.7 ± 0.1) × 10(6) L mol(-1) s(-1) for methyl linoleate to (2.7 ± 0.2) × 10(7) L mol(-1) s(-1) for methyl docosahexanoate at 25.0 ± 0.2 °C in ethanol. The apparent second-order rate constant for polyunsaturated fatty acid methyl ester oxidation by HER is dependent on the number of bisallylic hydrogen atoms rather than on the bond dissociation energy value for the weakest C-H bond as determined by ab initio density functional theory calculations. Sterols displayed higher reactivity compared to unsaturated fatty acid methyl esters with apparent second-order rate constants of (2.7 ± 0.1) × 10(6) and (5.2 ± 0.1) × 10(7) L mol(-1) s(-1) at 25.0 ± 0.2 °C in ethanol for cholesterol and ergosterol, respectively. Similar experiments with prenylflavonoids as potential herbal chemopreventive agents for preventing alcoholic liver diseases yield apparent second-order rate constants close to the diffusion control with kapp values of (1.5 ± 0.2) and (3.6 ± 0.1) × 10(9) L mol(-1)s(-1) for 6-prenylnarigerin and xanthohumol at 25.0 ± 0.2 °C in ethanol solution, respectively. Polyunsaturated lipids were revealed to be highly reactive oxidizable substrates toward HER-induced oxidation in biological systems leading to damage of membranes and sensitive structures.