Adductome-based identification of lysine mono-methylation as a key post-translational protein modification in autoimmune diseases.

Posttranslational modifications (PTMs) of proteins are efficient biological mechanisms for expanding the genetic code and for regulating cellular physiology. However, there have been no systematic approaches to profile all the PTMs critical for autoreactive neoantigen production or the etiology and pathology of autoimmune diseases. In the present study, to gain insight into protein PTMs associated with systemic lupus erythematosus (SLE), we applied a mass spectrometry-based method for the comprehensive analysis of modified amino acids ("adductome").

The origin of hydroxy-cyclohexenone fatty acids from skin barrier protein and relevance to covalent binding of ceramides.

Lipid constituents of the skin permeability barrier include a portion of ceramides and fatty acids covalently bound to the barrier protein. The covalent binding requires enzymatic oxidation of linoleate (C18:2) esterified to skin-specific acylceramides, forming a reactive 9,10-epoxy-11E-13-keto derivative. Barrier proteins treated with alkali release the bound lipids and as described recently, including two prominent cyclic linoleate derivatives, C18 hydroxy-cyclohexenone fatty acids.

Dry Heating of Curcumin in the Presence of Basic Salts Yields Anti-inflammatory Dimerization Products.

Curcumin exerts some of its biological effects via degradation products formed by spontaneous oxidation at physiological, i.e., weakly basic, pH.

Seabuckthorn (Hippophae rhamnoides, L.) pulp oil prevents ultraviolet-induced damage in human fibroblasts.

Seabuckthorn pulp oil (SBO) is used in beauty products because of its rich lipophilic substances with high nutraceutical and cosmeceutical potential. However, the mechanism through which SBO enhances skin elasticity remains unclear. Therefore, in this study, we examined the anti-photoaging activity of SBO in normal human dermal fibroblasts (NHDF) under ultraviolet (UV) irradiation.

Isocitrate dehydrogenase 1 upregulation in urinary extracellular vesicles from proximal tubules of type 2 diabetic rats.

Diabetic nephropathy (DN) is a major cause of chronic kidney disease. Microalbuminuria is currently the most common non-invasive biomarker for the early diagnosis of DN. However, renal structural damage may have advanced when albuminuria is detected.

Eriodictyol and thymonin act as GPR35 agonists.

Although herbs and spices have been used in traditional medicine for more than a century owing to their health benefits, the associated underlying mechanism is still not clear. Since the G protein-coupled receptor 35 (GPR35) has been linked to exert various antioxidant and anti-inflammatory effects, we screened 19 different herbs and spices for possible GPR35 agonist(s) to understand the GPR35-dependent functions of herbs and spices. Among the screened extracts, the ethyl acetate extract of thyme exhibited a remarkable GPR35 agonistic activity.

The 5-lipoxygenase/cyclooxygenase-2 cross-over metabolite, hemiketal E, enhances VEGFR2 activation and promotes angiogenesis.

Consecutive oxygenation of arachidonic acid by 5-lipoxygenase and cyclooxygenase-2 yields the hemiketal eicosanoids, HKE and HKD. Hemiketals stimulate angiogenesis by inducing endothelial cell tubulogenesis in culture; however, how this process is regulated has not been determined. Here, we identify vascular endothelial growth factor receptor 2 (VEGFR2) as a mediator of HKE-induced angiogenesis in vitro and in vivo.

Biosynthetic Crossover of 5-Lipoxygenase and Cyclooxygenase-2 Yields 5-Hydroxy-PGE and 5-Hydroxy-PGD.

The biosynthetic crossover of 5-lipoxygenase (5-LOX) and cyclooxygenase-2 (COX-2) enzymatic activities is a productive pathway to convert arachidonic acid into unique eicosanoids. Here, we show that COX-2 catalysis with 5-LOX derived 5-hydroxy-eicosatetraenoic acid yields the endoperoxide 5-hydroxy-PGH that spontaneously rearranges to 5-OH-PGE and 5-OH-PGD, the 5-hydroxy analogs of arachidonic acid derived PGE and PGD. The endoperoxide was identified via its predicted degradation product, 5,12-dihydroxy-heptadecatri-6,8,10-enoic acid, and by SnCl-mediated reduction to 5-OH-PGF.

Sodium sulfite causes gastric mucosal cell death by inducing oxidative stress.

Sulfites are commonly used as a preservative and antioxidant additives in the food industry. Sulfites are absorbed by the gastrointestinal tract and distributed essentially to all body tissues. Although sulfites have been believed to be safe food additives, some studies have shown that they exhibit adverse effects in various tissues.

Mechanistic Differences in the Inhibition of NF-κB by Turmeric and Its Curcuminoid Constituents.

Turmeric extract, a mixture of curcumin and its demethoxy (DMC) and bisdemethoxy (BDMC) isomers, is used as an anti-inflammatory preparation in traditional Asian medicine. Curcumin is considered to be the major bioactive compound in turmeric but less is known about the relative anti-inflammatory potency and mechanism of the other components, their mixture, or the reduced in vivo metabolites. We quantified inhibition of the NF-κB pathway in cells, adduction to a peptide mimicking IκB kinase β, and the role of cellular glutathione as a scavenger of electrophilic curcuminoid oxidation products, suggested to be the active metabolites.

Transformation of Prostaglandin D to 11-Dehydro Thromboxane B by Baeyer-Villiger Oxidation.

Prostaglandin D is one of five chief prostanoids formed in the cyclooxygenase pathway of arachidonic acid oxidation. Except for a single oxygen atom, PGD is structurally identical to 11-dehydro thromboxane B (11d-TxB ), a urinary metabolite of the pro-aggregatory platelet activator, thromboxane A . The close structural relationship suggested that one might be transformed to the other.

A unique mechanism for thiolation of serum albumins by disulphide molecules.

Protein S-thiolation is a reversible oxidative modification that serves as an oxidative regulatory mechanism for certain enzymes and binding proteins with reactive cysteine residues. It is generally believed that the thiolation occurs at free sulphydryl group of cysteine residues. Meanwhile, despite the fact that disulphide linkages, serving structural and energetic roles in proteins, are stable and inert to oxidative modification, a recent study shows that the thiolation could also occur at protein disulphide linkages when human serum albumin (HSA) was treated with disulphide molecules, such as cystine and homocystine.

Curcumin induces secretion of glucagon-like peptide-1 through an oxidation-dependent mechanism.

Curcumin shows antiglycemic effects in animals. Curcumin is chemically unstable at physiological pH, and its oxidative degradation products were shown to contribute to its anti-inflammatory effects. Since the degradation products may also contribute to other effects, we analyzed their role in the antiglycemic activity of curcumin.

A Dual Perspective of the Action of Lysine on Soybean Oil Oxidation Process Obtained by Combining H NMR and LC-MS: Antioxidant Effect and Generation of Lysine-Aldehyde Adducts.

Little is still known about both the effect of amino acids on the oxidation course of edible oils and the modifications that the former may undergo during this process. Bearing this in mind, the objective of this work was to study the evolution of a system consisting of soybean oil with 2% of l-lysine under heating at 70 °C and stirring conditions, analyzing how the co-oxidation of the oil and of the amino acid affects their respective evolutions, and trying to obtain information about the action mechanism of lysine on soybean oil oxidation. The study of the oil progress by H Nuclear Magnetic Resonance (H NMR) showed that the presence of lysine noticeably delays oil degradation and oxidation products generation in comparison with a reference oil without lysine.

Structural and functional insights into S-thiolation of human serum albumins.

Human serum albumin (HSA) is the most abundant serum protein, contributing to the maintenance of redox balance in the extracellular fluids. One single free cysteine residue at position 34 is believed to be a target of oxidation. However, the molecular details and functions of oxidized HSAs remain obscure.

Adductome-based identification of biomarkers for lipid peroxidation.

Lipid peroxidation is an endogenous source of aldehydes that gives rise to covalent modification of proteins in various pathophysiological states. In this study, a strategy for the comprehensive detection and comparison of adducts was applied to find a biomarker for lipid peroxidation-modified proteins This adductome approach utilized liquid chromatography with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) methods designed to detect the specific product ions from positively ionized adducts in a selected reaction monitoring mode. Using this procedure, we comprehensively analyzed lysine and histidine adducts generated in the oxidized low-density lipoproteins (LDL) and observed a prominent increase in several adducts, including a major lysine adduct.

Oxidative metabolism of curcumin-glucuronide by peroxidases and isolated human leukocytes.

Conjugation with glucuronic acid is a prevalent metabolic pathway of orally administrated curcumin, the bioactive diphenol of the spice turmeric. The major in vitro degradation reaction of curcumin is autoxidative transformation resulting in oxygenation and cyclization of the heptadienedione chain to form cyclopentadione derivatives. Here we show that curcumin-glucuronide is much more stable than curcumin, degrading about two orders of magnitude slower.

Oxidative Deamination of Serum Albumins by (-)-Epigallocatechin-3-O-Gallate: A Potential Mechanism for the Formation of Innate Antigens by Antioxidants.

(-)-Epigallocatechin-3-O-gallate (EGCG), the most abundant polyphenol in green tea, mediates the oxidative modification of proteins, generating protein carbonyls. However, the underlying molecular mechanism remains unclear. Here we analyzed the EGCG-derived intermediates generated upon incubation with the human serum albumin (HSA) and established that EGCG selectively oxidized the lysine residues via its oxidative deamination activity.

Identification of a prostaglandin D2 metabolite as a neuritogenesis enhancer targeting the TRPV1 ion channel.

Mast cells play important roles in allergic inflammation by secreting various mediators. In the present study, based on the finding that the medium conditioned by activated RBL-2H3 mast cells enhanced the nerve growth factor (NGF)-induced neuritogenesis of PC12 cells, we attempted to isolate an active compound from the mast cell conditioned culture medium. Our experiment identified 15-deoxy-Δ(12,14)-PGJ2 (15d-PGJ2), one of the PGD2 metabolites, as a potential enhancer of neuritogenesis.

Identification of C1q as a Binding Protein for Advanced Glycation End Products.

Advanced glycation end products (AGEs) make up a heterogeneous group of molecules formed from the nonenzymatic reaction of reducing sugars with the free amino groups of proteins. The abundance of AGEs in a variety of age-related diseases, including diabetic complications and atherosclerosis, and their pathophysiological effects suggest the existence of innate defense mechanisms. Here we examined the presence of serum proteins that are capable of binding glycated bovine serum albumin (AGEs-BSA), prepared upon incubation of BSA with dehydroascorbate, and identified complement component C1q subcomponent subunit A as a novel AGE-binding protein in human serum.

Functional interaction between cyclooxygenase-2 and p53 in response to an endogenous electrophile.

Cyclooxygenase-2 (Cox-2) is rapidly expressed by various stimuli and plays a key role in conversion of free arachidonic acid to prostaglandins. We have previously identified 4-hydroxy-2-nonenal (HNE), a lipid peroxidation-derived electrophile, as the potent Cox-2 inducer in rat epithelial RL34 cells and revealed that the HNE-induced Cox-2 expression resulted from the stabilization of Cox-2 mRNA that is mediated by the p38 mitogen-activated protein kinase signaling pathway. In the present study, we investigated an alternative regulatory mechanism of Cox-2 expression mediated by a transcription factor p53.

Toll-like receptors as a target of food-derived anti-inflammatory compounds.

Toll-like receptors (TLRs) play a key role in linking pathogen recognition with the induction of innate immunity. They have been implicated in the pathogenesis of chronic inflammatory diseases, representing potential targets for prevention/treatment. Vegetable-rich diets are associated with the reduced risk of several inflammatory disorders.

Lysine pyrrolation is a naturally-occurring covalent modification involved in the production of DNA mimic proteins.

Covalent modification of proteins exerts significant effects on their chemical properties and has important functional and regulatory consequences. We now report the identification and verification of an electrically-active form of modified proteins recognized by a group of small molecules commonly used to interact with DNA. This previously unreported property of proteins was initially discovered when the γ-ketoaldehydes were identified as a source of the proteins stained by the DNA intercalators.