Differential distribution of 4-hydroxynonenal adducts to sulfur and nitrogen residues in blood proteins as revealed using Raney nickel and gas chromatography-mass spectrometry

How lipids, as important endogenous nutrient components, affect the quality of aquatic products: An overview of lipid peroxidation and the interaction with proteins

As the global population continues to grow and the pressure on livestock and poultry supply increases, the oceans have become an increasingly important source of quality food for future generations. However, nutrient-rich aquatic product is susceptible to lipid oxidation during storage and transport, reducing its nutritional value and increasing safety risks. Therefore, identifying the specific effects of lipid oxidation on aquatic products has become particularly critical. At the same time, some lipid oxidation products have been found to interact with aquatic product proteins in various ways, posing a safety risk. This paper provides an in-depth exploration of the pathways, specific effects, and hazards of lipid oxidation in aquatic products, with a particular focus on the interaction of lipid oxidation products with proteins. Additionally, it discusses the impact of non-thermal treatment techniques on lipids in aquatic products and examines the application of natural antioxidants in aquatic products. Future research endeavors should delve into the interactions between lipids and proteins in these products and their specific effects to mitigate the impact of non-thermal treatment techniques on lipids, thereby enhancing the safety of aquatic products and ensuring food safety for future generations.

The 4-Hydroxynonenal–Protein Adducts and Their Biological Relevance: Are Some Proteins Preferred Targets?

It is well known that oxidative stress and lipid peroxidation (LPO) play a role in physiology and pathology. The most studied LPO product with pleiotropic capabilities is 4-hydroxynonenal (4-HNE). It is considered as an important mediator of cellular signaling processes and a second messenger of reactive oxygen species. The effects of 4-HNE are mainly attributed to its adduction with proteins. Whereas the Michael adducts thus formed are preferred in an order of potency of cysteine > histidine > lysine over Schiff base formation, it is not known which proteins are the preferred targets for 4-HNE under what physiological or pathological conditions. In this review, we briefly discuss the methods used to identify 4-HNE–protein adducts, the progress of mass spectrometry in deciphering the specific protein targets, and their biological relevance, focusing on the role of 4-HNE protein adducts in the adaptive response through modulation of the NRF2/KEAP1 pathway and ferroptosis.

The OSE complotype and its clinical potential

Cellular death, aging, and tissue damage trigger inflammation that leads to enzymatic and non-enzymatic lipid peroxidation of polyunsaturated fatty acids present on cellular membranes and lipoproteins. This results in the generation of highly reactive degradation products, such as malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE), that covalently modify free amino groups of proteins and lipids in their vicinity. These newly generated neoepitopes represent a unique set of damage-associated molecular patterns (DAMPs) associated with oxidative stress termed oxidation-specific epitopes (OSEs). OSEs are enriched on oxidized lipoproteins, microvesicles, and dying cells, and can trigger sterile inflammation. Therefore, prompt recognition and removal of OSEs is required to maintain the homeostatic balance. This is partially achieved by various humoral components of the innate immune system, such as natural IgM antibodies, pentraxins and complement components that not only bind OSEs but in some cases modulate their pro-inflammatory potential. Natural IgM antibodies are potent complement activators, and 30% of them recognize OSEs such as oxidized phosphocholine (OxPC-), 4-HNE-, and MDA-epitopes. Furthermore, OxPC-epitopes can bind the complement-activating pentraxin C-reactive protein, while MDA-epitopes are bound by C1q, C3a, complement factor H (CFH), and complement factor H-related proteins 1, 3, 5 (FHR-1, FHR-3, FHR-5). In addition, CFH and FHR-3 are recruited to 2-(ω-carboxyethyl)pyrrole (CEP), and full-length CFH also possesses the ability to attenuate 4-HNE-induced oxidative stress. Consequently, alterations in the innate humoral defense against OSEs predispose to the development of diseases associated with oxidative stress, as shown for the prototypical OSE, MDA-epitopes. In this mini-review, we focus on the mechanisms of the accumulation of OSEs, the pathophysiological consequences, and the interactions between different OSEs and complement components. Additionally, we will discuss the clinical potential of genetic variants in OSE-recognizing complement proteins – the OSE complotype - in the risk estimation of diseases associated with oxidative stress.

Computational Elucidation of the Solvent-Dependent Addition of 4-Hydroxy-2-nonenal (HNE) to Cysteine and Cysteinate Residues

The lipid peroxidation end product, 4-hydroxy-2-nonenal (HNE), is a secondary mediator of oxidative stress due to its strong ability to form adducts to the side chains of lysine, histidine, and cysteine residues (Cys) at increasing reactivities. This reaction can take place in various cellular environments and may be dependent on solvent. Moreover, approximately 10% of cysteine residues within the cells exist as the negatively charged cysteinate, which may also have a distinct reactivity toward HNE. In this study, quantum chemical calculations are used to investigate the reactivity of HNE toward Cys and cysteinate in three distinct solvent environments to mimic the aqueous, polar, and hydrophobic regions within the cell. Water enhances the reactivity of HNE to cysteine compared to that of the polar and hydrophobic solvents, and the reactivity of HNE is further augmented when Cys is first ionized to cysteinate. This is also confirmed by the transition state rate constant calculations. This study reveals the role of solvent polarity in these reactions and how cysteinate can account for the seemingly high reactivity of HNE toward Cys compared to other amino acid residues and demonstrates how a strong nucleophile can enhance the reactivity of an antioxidant analogue of the Cys residue.

Modification of proteins by reactive lipid oxidation products and biochemical effects of lipoxidation

Lipid oxidation results in the formation of many reactive products, such as small aldehydes, substituted alkenals, and cyclopentenone prostaglandins, which are all able to form covalent adducts with nucleophilic residues of proteins. This process is called lipoxidation, and the resulting adducts are called advanced lipoxidation end products (ALEs), by analogy with the formation of advanced glycoxidation end products from oxidized sugars. Modification of proteins by reactive oxidized lipids leads to structural changes such as increased β-sheet conformation, which tends to result in amyloid-like structures and oligomerization, or unfolding and aggregation. Reaction with catalytic cysteines is often responsible for the loss of enzymatic activity in lipoxidized proteins, although inhibition may also occur through conformational changes at more distant sites affecting substrate binding or regulation. On the other hand, a few proteins are activated by lipoxidation-induced oligomerization or interactions, leading to increased downstream signalling. At the cellular level, it is clear that some proteins are much more susceptible to lipoxidation than others. ALEs affect cell metabolism, protein-protein interactions, protein turnover via the proteasome, and cell viability. Evidence is building that they play roles in both physiological and pathological situations, and inhibiting ALE formation can have beneficial effects.

Plasma indicators of bovine health: Impacts of diet supplementations and pre-slaughter stress

This data article reports the values of indicators of bovine health determined in the plasma of Normand cull-cows at different times of the about 100 days lasting finishing period and at slaughter. The data constitute a large dataset based on the quantification of metabolites and the evaluation of enzymes activities allowing the determination of antioxidant capacity, oxidative stress level, energy and lipid metabolisms, activity of the Hypothalamo-Pituitary-Adrenal axis and the hepatic status in cull-cows.

Targeting Colon Luminal Lipid Peroxidation Limits Colon Carcinogenesis Associated with Red Meat Consumption

Red meat is probably carcinogenic to humans (WHO/IARC class 2A), in part through heme iron-induced lipoperoxidation. Here, we investigated whether red meat promotes carcinogenesis in rodents and modulates associated biomarkers in volunteers, speculating that an antioxidant marinade could suppress these effects via limitation of the heme induced lipid peroxidation. We gave marinated or non-marinated beef with various degrees of cooking to azoxymethane-initiated rats, Min mice, and human volunteers (crossover study). Mucin-depleted foci were scored in rats, adenoma in Min mice. Biomarkers of lipoperoxidation were measured in the feces and urine of rats, mice, and volunteers. The organoleptic properties of marinated meat were tested. Fresh beef increased colon carcinogenesis and lipoperoxidation in rats and mice and lipoperoxidation in humans. Without an adverse organoleptic effect on meat, marinade normalized peroxidation biomarkers in rat and mouse feces, reduced peroxidation in human feces and reduced the number of Mucin-depleted foci in rats and adenoma in female Min mice. This could lead to protective strategies to decrease the colorectal cancer burden associated with red meat consumption. Cancer Prev Res; 11(9); 569-80. ©2018 AACR.

4-Hydroxynonenal (HNE) modified proteins in metabolic diseases

4-Hydroxynonenal (HNE) is one of the quantitatively most important products of lipid peroxidation. Due to its high toxicity it is quickly metabolized, however, a small share of HNE avoids enzymatic detoxification and reacts with biomolecules including proteins. The formation of HNE-protein-adducts is one of the accompanying processes in oxidative stress or redox disbalance. The modification of proteins might occur at several amino acids side chains, leading to a variety of products and having effects on the protein function and fate. This review summarizes current knowledge on the formation of HNE-modified proteins, their fate in mammalian cells and their potential role as a damaging agents during oxidative stress. Furthermore, the potential of HNE-modified proteins as biomarkers for several diseases are highlighted.

Quantification of 4-hydroxy-2-nonenal-protein adducts in the in vivo gastric digesta of mini-pigs using a GC-MS/MS method with accuracy profile validation

Hydroxyalkenals are lipid oxidation end-products resulting from the oxidation of polyunsaturated fatty acids (PUFA). This study aimed at quantifying the production of 4-hydroxy-2-nonenal-protein adducts (HNE-P) via Michael addition from n-6 PUFA oxidation in the gastric digesta of mini-pigs after the consumption of meat-based meals with different plant antioxidant contents. Using the accuracy profile procedure, we validated an extraction protocol for the quantification of HNE-P by GC-MS/MS in gastric contents. The formation of HNE-P in the gastric compartment was observed for the first time, with concentrations ranging from less than 0.52 to 1.33 nmol HNE-P per 500 mg digesta. Nevertheless, most gastric HNE-P levels were below the limit of quantification of 0.52 nmol HNE-P per 500 mg digesta. In this animal study, the protective effect of plant antioxidant sources on HNE-P formation was not evidenced contrasting with the results using TBARS as markers.

Red meat and colorectal cancer: Nrf2-dependent antioxidant response contributes to the resistance of preneoplastic colon cells to fecal water of hemoglobin- and beef-fed rats

Epidemiological studies have associated red meat intake with risk of colorectal cancer. Experimental studies explain this positive association by the oxidative properties of heme iron released in the colon. This latter is a potent catalyst for lipid peroxidation, resulting in the neoformation of deleterious aldehydes in the fecal water of heme-fed rats. The toxicity of fecal water of heme-fed rats was associated to such lipid peroxidation. This study demonstrated that fecal water of hemoglobin- and beef-fed rats preferentially induced apoptosis in mouse normal colon epithelial cells than in those carrying mutation on Apc (Adenomatous polyposis coli) gene, considered as preneoplastic. Highlighting the importance of lipid peroxidation and neoformation of secondary aldehydes like 4-hydroxy-2-nonenal (HNE), we optimized the depletion of carbonyl compounds in the fecal water which turned out to abolish the differential apoptosis in both cell lines. To explain the resistance of preneoplastic cells towards fecal water toxicity, we focused on Nrf2, known to be activated by aldehydes, including HNE. Fecal water activated Nrf2 in both cell lines, associated with the induction of Nrf2-target genes related to aldehydes detoxification. However, the antioxidant defense appeared to be higher in preneoplastic cells, favoring their survival, as evidenced by Nrf2 inactivation. Taken together, our results suggest that Nrf2-dependent antioxidant response was involved in the resistance of preneoplastic cells upon exposure to fecal water of hemoglobin- and beef-fed rats. This difference could explain the promoting effect of red meat and heme-enriched diet on colorectal cancer, by initiating positive selection of preneoplastic cells.

Circulating levels of linoleic acid and HDL-cholesterol are major determinants of 4-hydroxynonenal protein adducts in patients with heart failure

OBJECTIVE

Measurements of oxidative stress biomarkers in patients with heart failure (HF) have yielded controversial results. This study aimed at testing the hypothesis that circulating levels of the lipid peroxidation product 4-hydroxynonenal bound to thiol proteins (4HNE-P) are strongly associated with those of its potential precursors, namely n-6 polyunsaturated fatty acids (PUFA).

METHODS AND RESULTS

Circulating levels of 4HNE-P were evaluated by gas chromatography-mass spectrometry in 71 control subjects and 61 ambulatory symptomatic HF patients along with various other clinically- and biochemically-relevant parameters, including other oxidative stress markers, and total levels of fatty acids from all classes, which reflect both free and bound to cholesterol, phospholipids and triglycerides. All HF patients had severe systolic functional impairment despite receiving optimal evidence-based therapies. Compared to controls, HF patients displayed markedly lower circulating levels of HDL- and LDL-cholesterol, which are major PUFA carriers, as well as of PUFA of the n-6 series, specifically linoleic acid (LA; P=0.001). Circulating 4HNE-P in HF patients was similar to controls, albeit multiple regression analysis revealed that LA was the only factor that was significantly associated with circulating 4HNE-P in the entire population (R (2)=0.086; P=0.02). In HF patients only, 4HNE-P was even more strongly associated with LA (P=0.003) and HDL-cholesterol (p<0.0002). Our results demonstrate that 4HNE-P levels, expressed relative to HDL-cholesterol, increase as HDL-cholesterol plasma levels decrease in the HF group only.

CONCLUSION

Results from this study emphasize the importance of considering changes in lipids and lipoproteins in the interpretation of measurements of lipid peroxidation products. Further studies appear warranted to explore the possibility that HDL-cholesterol particles may be a carrier of 4HNE adducts.

Advances in purification and separation of posttranslationally modified proteins

Posttranslational modifications (PTMs) of proteins represent fascinating extensions of the dynamic complexity of living cells' proteomes. The results of enzymatically catalyzed or spontaneous chemical reactions, PTMs form a fourth tier in the gene - transcript - protein cascade, and contribute not only to proteins' biological functions, but also to challenges in their analysis. There have been tremendous advances in proteomics during the last decade. Identification and mapping of PTMs in proteins have improved dramatically, mainly due to constant increases in the sensitivity, speed, accuracy and resolution of mass spectrometry (MS). However, it is also becoming increasingly evident that simple gel-free shotgun MS profiling is unlikely to suffice for comprehensive detection and characterization of proteins and/or protein modifications present in low amounts. Here, we review current approaches for enriching and separating posttranslationally modified proteins, and their MS-independent detection. First, we discuss general approaches for proteome separation, fractionation and enrichment. We then consider the commonest forms of PTMs (phosphorylation, glycosylation and glycation, lipidation, methylation, acetylation, deamidation, ubiquitination and various redox modifications), and the best available methods for detecting and purifying proteins carrying these PTMs. This article is part of a Special Issue entitled: Posttranslational Protein modifications in biology and Medicine.

4-HNE adduct stability characterized by collision-induced dissociation and electron transfer dissociation mass spectrometry

4-Hydroxynonenal (4-HNE) alters numerous proteomic and genomic processes. Understanding chemical mechanisms of 4-HNE interactions with biomolecules and their respective stabilities may lead to new discoveries in biomarkers for numerous diseases of oxidative stress. Collision-induced dissociation (CID) and electron transfer dissociation (ETD) MS/MS were utilized to examine the stability of a 4-HNE-Cys Michael adduct. CID conditions resulted in the neutral loss of 4-HNE, also known as a retro-Michael addition reaction (RMA). Consequently, performing ETD fragmentation on this same adduct did not result in RMA. Interestingly, 4-HNE adduct reduction via sodium borohydride (NaBH₄) treatment stabilized against the CID induced RMA. In a direct comparison of three forms of 4-HNE adducts, computational modeling revealed sizable shifts in the shape and orientation of the lowest unoccupied molecular orbital (LUMO) density around the 4-HNE-Cys moiety. These findings demonstrate that ETD MS/MS analysis can be used to improve the detection of 4-HNE-protein modifications by preventing RMA reactions from occurring.

Ferulic acid ethyl ester as a potential therapy in neurodegenerative disorders

Oxidative stress is involved in the onset, progression and pathogenesis of a number of diseases including neurodegenerative diseases. It is critical to develop a pharmacological approach to combat oxidative stress which may reduce the risk of diseases and help in promoting healthy life. In an attempt to reduce the side effects associated with allopathic medicines a number of studies are now focusing on developing treatment regimens from naturally occurring plant products. In this review, the protective role of ferulic acid (4-hydroxy-3-methoxycinnamic acid) (FA), a naturally occurring antioxidant compound found in fruit, some vegetables, and grains, and its ethyl ester derivative are discussed with respect to neurodegeneration. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.