Aggregation of α- and β- caseins induced by peroxyl radicals involves secondary reactions of carbonyl compounds as well as di-tyrosine and di-tryptophan formation

The extracellular matrix (ECM) of tissues is susceptible to modification by inflammation-associated oxidants. Considerable data support a role for hypochlorous acid (HOCl), generated by the leukocytederived heme-protein myeloperoxidase (MPO) in these changes. HOCl can modify isolated ECM proteins and cell-derived matrix, with this resulting in decreased cell adhesion, modulated proliferation and gene expression, and phenotypic changes. Whether this arises from free HOCl, or via site-specific reactions is unresolved. Here we examine the mechanisms of MPO-mediated changes to human coronary smooth muscle cell ECM. MPO is shown to co-localize with matrix fibronectin as detected by confocal microscopy, and bound active MPO can initiate ECM modification, as detected by decreased antibody recognition of fibronectin, versican and type IV collagen, and formation of protein carbonyls and HOCl-mediated damage. These changes are recapitulated by a glucose/glucose oxidase/MPO system where low continuous fluxes of H 2 o 2 are generated. HOCl-induced modifications enhance Mpo binding to ecM proteins as detected by eLiSA and Mpo activity measurements. these data demonstrate that MPO-generated HOCl induces ECM modification by interacting with ECM proteins in a site-specific manner, and generates alterations that increase MPO adhesion. This is proposed to give rise to an increasing cycle of alterations that contribute to tissue damage.The extracellular matrix (ECM) is essential for the homeostasis of tissues. In the case of the artery wall, the vascular basement membrane plays a key role in supporting and determining endothelial and smooth muscle cell survival and function 1 . This ECM forms a specialized and distinct microenvironment, with the biomacromolecules (e.g., collagens, laminins, fibronectin, perlecan, versican, elastin, nidogen, syndecans) that comprise this material, and a myriad of associated materials (e.g., cytokines, growth factors) dictating the shape and function of the artery wall, and the nature and behavior of the associated vascular cells 2 . Due to the lower turnover rate of many ECM materials (cf. estimated half-lives of 60-70 days and 74 years for arterial collagen and elastin, respectively 3,4 ), and the low levels of antioxidant defense systems in extracellular environments 5 , ECM components and proteins in biological fluids appear to be particularly susceptible to oxidant damage. These factors result in a gradual accumulation of damage in the ECM with both aging and disease, including within the artery wall during the development of atherosclerosis (reviewed 2,6 ). At least some of this damage appears to arise via the formation of oxidants generated by the leukocyte-derived heme enzyme myeloperoxidase (MPO) 7 .Alterations to the structure and properties of ECM has been associated with the progression of atherosclerosis 8 . Previous studies have shown that approximately 70% of the oxidation products detected on proteins extracted from human atherosclerotic lesions are present on ECM proteins 7 , consist...

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“…Such reactions have been reported previously to contribute to inter-molecular protein cross-linking (e.g. 54 ).…”

supporting

confidence: 62%

Binding of myeloperoxidase to the extracellular matrix of smooth muscle cells and subsequent matrix modification

Cai

Chuang

Hawkins

et al. 2020

Sci Rep

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“…Some of these species are consistent with the species detected on isolated whey proteins exposed to specific oxidant systems (e.g. heat/H 2 O 2 and also light in the presence of riboflavin) [46,47,52,60,61]. A number of the species detected are consistent with the occurrence of radical reactions (e.g.…”

Section: Presence Of Oxidation Glycation and Racemised Whey Proteinsupporting

confidence: 81%

Whey proteins: targets of oxidation, or mediators of redox protection

Giblin

Yalçın

Biçim

et al. 2019

Free Radical Research

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Bovine whey proteins are highly valued dairy ingredients. This is primarily due to their amino acid content, digestibility, bioactivities and their processing characteristics. One of the reported bioactivities of whey proteins is antioxidant activity. Numerous dietary intervention trials with humans and animals indicate that consumption of whey products can modulate redox biomarkers to reduce oxidative stress. This bioactivity has in part been assigned to whey peptides using a range of biochemical or cellular assays in vitro. Superimposing whey peptide sequences from gastrointestinal samples, with whey peptides proven to be antioxidant in vitro, allows us to propose peptides from whey likely to exhibit antioxidant activity in the diet. However, whey proteins themselves are targets of oxidation during processing particularly when exposed to high thermal loads and/or extensive processing (e.g. infant formula manufacture). Oxidative damage of whey proteins can be selective with regard to the residues that are modified and are associated with the degree of protein unfolding, with a-Lactalbumin more susceptible than b-Lactoglobulin. Such oxidative damage may have adverse effects on human health. This review summarises how whey proteins can modulate cellular redox pathways and conversely how whey proteins can be oxidised during processing. Given the extensive processing steps that whey proteins are often subjected to, we conclude that oxidation during processing is likely to compromise the positive health attributes associated with whey proteins.

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“…These methods allow (approximate) quantification of the total cross-link yield, but not positional data. The low levels of Tyr-Tyr detected in some studies with high levels of oligomerization indicate that other species must also play a major role in the detected aggregation (252).…”

Section: Detection and Quantification Of Productsmentioning

confidence: 95%

Detection, identification, and quantification of oxidative protein modifications

Hawkins

Davies

2019

Journal of Biological Chemistry

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314

209

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Edited by Ruma Banerjee 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.

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Aggregation of α- and β- caseins induced by peroxyl radicals involves secondary reactions of carbonyl compounds as well as di-tyrosine and di-tryptophan formation

Cited by 33 publications

References 49 publications

Binding of myeloperoxidase to the extracellular matrix of smooth muscle cells and subsequent matrix modification

Binding of myeloperoxidase to the extracellular matrix of smooth muscle cells and subsequent matrix modification

Whey proteins: targets of oxidation, or mediators of redox protection

Detection, identification, and quantification of oxidative protein modifications

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