Dityrosine Research Articles

Novel Properties of Old Propranolol-Assessment of Antiglycation Activity through In Vitro and In Silico Approaches.

Hypertension has earned the "silent killer" nickname since it may lead to a number of comorbidities, including diabetes and cardiovascular diseases. Oxidative stress and protein glycation play vital roles in the pathogenesis of hypertension. Several studies have shown that they profoundly account for vascular dysfunction, endothelial damage, and disruption of blood pressure regulatory mechanisms. Of particular note are advanced glycation end products (AGEs). AGEs alter vascular tissues' functional and mechanical properties by binding to receptors for advanced glycation end products (RAGE), stimulating inflammation and free radical-mediated pathways. Propranolol, a nonselective beta-adrenergic receptor antagonist, is one of the most commonly used drugs to treat hypertension and cardiovascular diseases. Our study is the first to analyze propranolol's effects on protein glycoxidation through in vitro and in silico approaches. Bovine serum albumin (BSA) was utilized to evaluate glycoxidation inhibition by propranolol. Propranolol (1 mM) and BSA (0.09 mM) were incubated with different glycating (0.5 M glucose, fructose, and galactose for 6 days and 2.5 mM glyoxal and methylglyoxal for 12 h) or oxidizing agents (chloramine T for 1 h). Biomarkers of protein glycation (Amadori products (APs), β-amyloid (βA), and advanced glycation end products (AGEs)), protein glycoxidation (dityrosine (DT), kynurenine (KYN), and N-formylkynurenine (NFK)), protein oxidation (protein carbonyls (PCs), and advanced oxidation protein products (AOPPs)) were measured by means of colorimetric and fluorimetric methods. The scavenging of reactive oxygen species (hydrogen peroxide, hydroxyl radical, and nitric oxide) and the antioxidant capacity (2,2-diphenyl-1-picrylhydrazyl radical and ferrous ion chelating (FIC) assays)) of propranolol were also evaluated. Additionally, in silico docking was performed to showcase propranolol's interaction with BSA, glycosides, and AGE/RAGE pathway proteins. The products of protein glycation (↓APs, ↓βA, ↓AGEs), glycoxidation (↓DT, ↓KYN, ↓NFK), and oxidation (↓PCs, ↓AOPPs) prominently decreased in the BSA samples with both glycating/oxidizing factors and propranolol. The antiglycoxidant properties of propranolol were similar to those of aminoguanidine, a known protein oxidation inhibitor, and captopril, which is an established antioxidant. Propranolol showed a potent antioxidant activity in the FIC and H2O2 scavenging assays, comparable to aminoguanidine and captopril. In silico analysis indicated propranolol's antiglycative properties during its interaction with BSA, glycosidases, and AGE/RAGE pathway proteins. Our results confirm that propranolol may decrease protein oxidation and glycoxidation in vitro. Additional studies on human and animal models are vital for in vivo verification of propranolol's antiglycation activity, as this discovery might hold the key to the prevention of diabetic complications among cardiology-burdened patients.

Effectiveness of lycopene dietary enrichment for growth performance, digestive enzymes, blood health, immunity, and antioxidant status of common carp (Cyprinus carpio) against chronic glyphosate toxicity

For food safety challenges, sustainable aquaculture emerges as a significant source in recent years; however, despite its potential, the industry still facing challenges, notably the exposure of cultured animals to pesticidal pollution. This pollution originating from agricultural practices that can enter aquaculture system directly: to integrated-agriculture aquaculture practices, or indirectly via soil leakage. Current research based on glyphosate (GLY) toxicity and its amelioration by lycopene (LYC). Four fish groups used for six-weeks experiment in which four groups were used. Control group (CL) was fed with basal commercial diet only without any LYC and GLY exposure; 2) LYC group: exposed to LYC supplemented diet (15 mg/kg per fish diet); 3) GLY group: exposed to glyphosate only (1/5th of 96 h LC50: 0.0892 mg/L) with basal commercial diet, and; 4) GLY + LYC group: exposed to both lycopene supplemented diet (15 mg/kg per fish diet) and glyphosate (1/5th of 96 h LC50: 0.0892 mg/L). GLY observed to decrease growth parameters and feed utilization whereas, lycopene ameliorated growth rate (WG, SGR, HSI, CF) and feeding utilization (FCR) as compared to the control group. Also, GLY induced toxicity within hematobiochemical parameters with alleviation by LYC supplementation. GLY induced cytotoxicity was observed within RBCs as lobbing, notching, vacuolation, blebbing, micronuclei, and condensation. Increase in reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) were observed by GLY exposure. Also, there is observed reduction in antioxidant enzyme activities (CAT, SOD, POD, TPC and GSH) upon GLY exposure. Lipid peroxidation (malondialdehyde: MDA), 8-OHdG (8-hydroxy-2′-deoxyguanosine) and DIY (dityrosine) observed to increase by GLY toxicity. There was improvement in immune responses; increased AChE (acetylcholinesterase) activity, lysozyme content, ACP (acid phosphatase), NBT (nitro blue tetrazolium), NO (nitric oxide) and IgM levels (immunoglobulin M) and digestive enzyme activities (protease, lipase and amylase) observed by LYC supplemented diet. Taken together, LYC supplementation observed to alleviate GLY induced oxidative stress and cytotoxicity with improved immunity, digestive actions and blood health within C. carpio. Therefore, dietary supplementation with lycopene can protect common carp from the harmful effects by glyphosate within agri-integrated aquaculture practices, so suggesting it as potential feed additive.

Validation of plasma protein glycation and oxidation biomarkers for the diagnosis of autism

Autism Spectrum Disorder (ASD) is a common neurodevelopmental disorder in children. It is currently diagnosed by behaviour-based assessments made by observation and interview. In 2018 we reported a discovery study of a blood biomarker diagnostic test for ASD based on a combination of four plasma protein glycation and oxidation adducts. The test had 88% accuracy in children 5–12 years old. Herein, we present an international multicenter clinical validation study (N = 478) with application of similar biomarkers to a wider age range of 1.5–12 years old children. Three hundred and eleven children with ASD (247 male, 64 female; age 5.2 ± 3.0 years) and 167 children with typical development (94 male, 73 female; 4.9 ± 2.4 years) were recruited for this study at Sidra Medicine and Hamad Medical Corporation hospitals, Qatar, and Hospital Regional Universitario de Málaga, Spain. For subjects 5–12 years old, the diagnostic algorithm with features, advanced glycation endproducts (AGEs)—Nε-carboxymethyl-lysine (CML), Nω-carboxymethylarginine (CMA) and 3-deoxyglucosone-derived hydroimidazolone (3DG-H), and oxidative damage marker, o,o’-dityrosine (DT), age and gender had accuracy 83% (CI 79 – 89%), sensitivity 94% (CI 90–98%), specificity 67% (CI 57–76%) and area-under-the-curve of receiver operating characteristic plot (AUROC) 0.87 (CI 0.84–0.90). Inclusion of additional plasma protein glycation and oxidation adducts increased the specificity to 74%. An algorithm with 12 plasma protein glycation and oxidation adduct features was optimum for children of 1.5–12 years old: accuracy 74% (CI 70–79%), sensitivity 75% (CI 63–87%), specificity 74% (CI 58–90%) and AUROC 0.79 (CI 0.74–0.84). We conclude that ASD diagnosis may be supported using an algorithm with features of plasma protein CML, CMA, 3DG-H and DT in 5–12 years-old children, and an algorithm with additional features applicable for ASD screening in younger children. ASD severity, as assessed by ADOS-2 score, correlated positively with plasma protein glycation adducts derived from methylglyoxal, hydroimidazolone MG-H1 and Nε(1-carboxyethyl)lysine (CEL). The successful validation herein may indicate that the algorithm modifiable features are mechanistic risk markers linking ASD to increased lipid peroxidation, neuronal plasticity and proteotoxic stress.

Plasma AGE and Oxidation Products, Renal Function, and Preeclampsia in Pregnant Women with Type 1 Diabetes: A Prospective Observational Study.

We aimed to determine whether plasma advanced glycation end products or oxidation products (AGE/oxidation-P) predict altered renal function and/or preeclampsia (PE) in pregnant women with type 1 diabetes. Prospectively, using a nested case-control design, we studied 47 pregnant women with type 1 diabetes, of whom 23 developed PE and 24 did not. Nineteen nondiabetic, normotensive pregnant women provided reference values. In plasma obtained at ~12, 22, and 32 weeks' gestation (visits 1, 2, and 3; V1-V3), we measured five AGE products (carboxymethyllysine (CML), carboxyethyl-lysine (CEL), methylglyoxal-hydroimidazolone (MGH1), 3-deoxyglucosone hydroimidazolone (3DGH), and glyoxal-hydroimidazolone (GH1)) and four oxidation products (methionine sulfoxide (MetSO), 2-aminoadipic acid (2-AAA), 3-nitrotyrosine (3NT), and dityrosine (DT)), by liquid chromatography/mass spectroscopy. Clinical outcomes were "estimated glomerular filtration rate" (eGFR) at each visit and onset of PE. In diabetic women, associations between AGE/oxidation-P and eGFR were found only in those who developed PE. In this group, CEL, MGH1, and GH1 at V2 and CML, CEL, MGH1, and GH1 at V3 were inversely associated with contemporaneous eGFR, while CEL, MGH1, 3DGH, and GH1 at V2 were inversely associated with eGFR at V3 (all p < 0.05). There were no associations of plasma AGE or oxidation-P with pregnancy-related development of proteinuria or PE. Inverse associations of second and early third trimester plasma AGE with eGFR among type 1 diabetic women who developed PE suggest that these patients constitute a subset susceptible to AGE-mediated injury and thus to cardiorenal complications later in life. However, AGE/oxidation-P did not predict PE in type 1 diabetic women.

Dietary Dityrosine Induces Oxidative Stress and Mitochondrial-Lipid Imbalance in Mouse Liver via MiR-144-3p-Mediated Downregulation of Nrf2.

Dityrosine (DT) is a protein oxidation marker present in many high-protein foods, such as dairy and meat products. Chronic dietary intake of DT induces oxidative stress damage in the liver and impairs energy metabolism. This study aims to investigate the mechanisms underlying the effects of DT on disrupted hepatic energy metabolism. The study investigates hepatic lipid accumulation, redox status imbalance, mitochondrial dysfunction, and energy metabolism disorders in 4-week-old C57BL/6J mice after 35 days of DT (420 µgkg-1 body weight) treatment. Transcriptome sequencing and quantitative real-time PCR in HepG2 cells show that DT mainly acted via miR-144-3p. miR-144-3p targets immune responsive gene 1 (IRG1) and decreases the fumaric acid level in the tricarboxylic acid (TCA) cycle, thereby decreasing nuclear factor erythroid 2-related factor 2 (Nrf2) expression and antioxidant activity. Administration of lycopene, a strong antioxidant, alleviates DT-induced damage in mice, confirming the involvement of the Nrf2 pathway in DT-induced abnormal hepatic lipid metabolism and energy homeostasis.

Chlorogenic Acid Attenuates Doxorubicin-Induced Oxidative Stress and Markers of Apoptosis in Cardiomyocytes via Nrf2/HO-1 and Dityrosine Signaling.

(1) Background: Doxorubicin (DOX) is extensively used for cancer treatments; however, its clinical application is limited because of its cardiotoxic adverse effects. A combination of DOX and agents with cardioprotective properties is an effective strategy to ameliorate DOX-related cardiotoxicity. Polyphenolic compounds are ideal for the investigation of novel cardioprotective agents. Chlorogenic acid (CGA), an essential dietary polyphenol found in plants, has been previously reported to exert antioxidant, cardioprotective, and antiapoptotic properties. The current research evaluated CGA's in vivo cardioprotective properties in DOX-induced cardiotoxicity and the probable mechanisms underlying this protection. (2) Methods: CGA's cardioprotective properties were investigated in rats that were treated with CGA (100 mg/kg, p.o.) for fourteen days. The experimental model of cardiotoxicity was induced with a single intraperitoneal (15 mg/kg i.p.) injection of DOX on the 10th day. (3) Results: Treatment with CGA significantly improved the DOX-caused altered cardiac damage markers (LDH, CK-MB, and cTn-T), and a marked improvement in cardiac histopathological features accompanied this. DOX downregulated the expression of Nrf2/HO-1 signaling pathways, and the CGA reversed this effect. Consistently, caspase-3, an apoptotic-related marker, and dityrosine expression were suppressed, while Nrf2 and HO-1 expressions were elevated in the cardiac tissues of DOX-treated rats after treatment with the CGA. Furthermore, the recovery was confirmed by the downregulation of 8-OHdG and dityrosine (DT) expressions in immunohistochemical findings. (4) Conclusions: CGA demonstrated a considerable cardioprotective effect against DOX-induced cardiotoxicity. One of the possible mechanisms for these protective properties was the upregulation of the Nrf2/HO-1-dependent pathway and the downregulation of DT, which may ameliorate oxidative stress and cardiomyocyte apoptosis. These findings suggest that CGA may be cardioprotective, particularly in patients receiving DOX-based chemotherapy.

Dityrosine cross-linking and its potential roles in Alzheimer's disease.

Oxidative stress is a significant source of damage that accumulates during aging and contributes to Alzheimer's disease (AD) pathogenesis. Oxidation of proteins can give rise to covalent links between adjacent tyrosines known as dityrosine (DiY) cross-linking, amongst other modifications, and this observation suggests that DiY could serve as a biomarker of accumulated oxidative stress over the lifespan. Many studies have focused on understanding the contribution of DiY to AD pathogenesis and have revealed that DiY crosslinks can be found in both Aβ and tau deposits - the two key proteins involved in the formation of amyloid plaques and tau tangles, respectively. However, there is no consensus yet in the field on the impact of DiY on Aβ and tau function, aggregation, and toxicity. Here we review the current understanding of the role of DiY on Aβ and tau gathered over the last 20 years since the first observation, and discuss the effect of this modification for Aβ and tau aggregation, and its potential as a biomarker for AD.

Preliminary Effects of Osteopathic Manipulative Medicine on Reactive Oxygen Species in Parkinson's Disease: A Randomized Controlled Pilot Study.

Context Parkinson's disease (PD) is the second most common neurodegenerative disorder and causes many clinical manifestations including bradykinesia, tremor, postural instability, and musculoskeletal stiffness. Neurodegeneration is commonly associated with oxidative stress. Oxidative stress has not been measured in PD in relation to the manual techniques used in Osteopathic Manipulative Treatment (OMT). Objective To investigate the effect of OMT on oxidative stress biomarkers in PD. Methods In this randomized non-blinded study, 32 PD subjects were separated by block randomization into counseling and OMT groups, receiving respective interventions twice a week for six weeks. The counseling arm received informative sessions while the OMT arm received a set treatment protocol. Biomarkers of oxidative stress, malondialdehyde (MDA), dityrosine (DT), 3-nitrotyrosine (3-NT), 8-hydroxy-2-deoxyguanosine (8-OHdG), and 8-isoprostane were measured before and after the first session and at weeks three, six, and 10 (four weeks after conclusion of intervention). Results No significant changes were found in blood plasma levels of MDA, DT, 3-NT, or 8-OHdG during or after intervention compared to controls (p > 0.05). No significant changes were found in urine 8-OHdG or 8-isoprostane during or after intervention compared to controls (p > 0.05). Conclusion OMT used in this study did not significantly affect the chosen oxidative stress biomarkers, however many limitations of the study may have impeded possible findings.

Determination of the Oxidative Stress Biomarkers of 8-Hydroxydeoxyguanosine and Dityrosine in the Gills, Skin, Dorsal Fin, and Liver Tissue of Atlantic Salmon (Salmo salar) Parr.

Oxidative stress is a condition caused by an imbalance in the occurrence of reactive oxygen species in the cells and tissues of organisms. An ultra-performance liquid chromatography–electrospray ionization tandem mass spectrometry (UPLC–ESI–MS/MS) method was developed for the simultaneous determination of two oxidative stress biomarkers, 8-hydroxydeoxyguanosine (8OHDG) and dityrosine (DIY), in the gills, skin, dorsal fin, and liver tissue of Atlantic salmon (Salmo salar) parr. The use of target analyte-specific 13C and 15N internal standards allowed quantification of each target analyte to be performed through the standard solvent calibration curve. The relative recoveries [mean ± (relative standard deviation%)] of 8OHDG and DIY were 101 ± 11 and 104 ± 13% at a fortified concentration of 10 ng/mL (8OHDG) and 500 ng/mL (DIY), respectively, ensuring the accuracy of the extraction and quantification. The chromatographic separation was carried out using a gradient elution program with a total run time of 5 min. The limits of detection (LODs) were 0.11 and 1.37 ng/g wet weight (w.w.) for 8OHDG and DIY, respectively. To demonstrate the applicability of the developed method, it was applied in 907 tissue samples that were collected from Atlantic salmon parr individuals reared in an experimental land-based recirculating aquaculture system (RAS) treated with peracetic acid. Moreover, the possibility of using the dorsal fin as an alternative matrix for the minimally invasive assessment of oxidative stress in Atlantic salmon parr was introduced. To our knowledge, 8OHDG and DIY were used for the first time as biomarkers for biomonitoring the fish health (oxidative stress) of Atlantic salmon parr in RAS.

Association of Vegetable and Fruit Consumption with Urinary Oxidative Biomarkers in Teenaged Girls: A School-Based Pilot Study in Japan.

Hexanoyl-lysine (HEL), 8-hydroxy-2′deoxyguanosine (8-OHdG), and dityrosine (DT) have served as potential biomarkers for detecting oxidative modified lipids, DNA, and proteins in biological samples, respectively. Whether regular higher levels of consumption of vegetables/fruit (V/F) would decrease oxidative modification of these biomolecules in the body remain unelucidated. To examine the association of regular V/F consumption with the generation of these reactive oxygen species-induced biomarkers, this study evaluated V/F consumption in a school-based sample of teenaged girls (mean age 15.6 ± 1.7 years, n = 103), and quantified the formation of oxidative stress biomarkers in their urine. Only 19.4% and 23.3% of participants reported that they consumed the recommended daily amount of vegetables and fruits, respectively. Individuals who consumed lower levels of fruit (<100g/day) or vegetables (<250g/day) had significantly higher HEL excretion in their urine than those who consumed higher levels of fruit (≥100g/day) (p < 0.05) or vegetables (≥250g/day) (p = 0.057). The results of a multiple regression analysis showed that vegetable consumption was an important inhibiting factor of early lipid peroxidation measured as HEL in urine, independent of various confounders (β = − 0.332, p < 0.05). The findings suggest that relatively higher consumption of vegetables would help in the prevention of early lipid peroxidation in adolescents.

Lycopene Regulates Dietary Dityrosine-Induced Mitochondrial-Lipid Homeostasis by Increasing Mitochondrial Complex Activity.

Dityrosine (DT), a marker of protein oxidation, is widely found in many high-protein foods. Dietary intake of DT induces myocardial oxidative stress injury and impairs energy metabolism. Lycopene is a common dietary supplement with antioxidant and mitochondrial-lipid homeostasis modulating abilities. This study aimed to examine the effects of lycopene on DT-induced disturbances in myocardial function and energy metabolism. Four-week-old C57BL/6J mice received intragastric administration of either tyrosine (420µg kg-1 BW), DT (420µg kg-1 BW), or lycopene at high (10mg kg-1 BW) and low (5mg kg-1 BW) doses for 35 days. Lycopene administration effectively reduced oxidative stress, cardiac fatty acid accumulation, and cardiac hypertrophy and improved mitochondrial performance in DT-induced mice. In vitro experiments in H9c2 cells showed that DT directly inhibited the activity of the respiratory chain complex, whereas oxidative phosphorylation and β-oxidation gene expression is upregulated. Lycopene enhanced the activity of the complexes and inhibited ROS production caused by compensatory regulation. Lycopene improves DT-mediated myocardial energy homeostasis disorder by promoting the activity of respiratory chain complexes I and IV and alleviates the accumulation of cardiac fatty acids and myocardial hypertrophy.

Di-Tyrosine Crosslinking and NOX4 Expression as Oxidative Pathological Markers in the Lungs of Patients with Idiopathic Pulmonary Fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a noninflammatory progressive lung disease. Oxidative damage is a hallmark of IPF, but the sources and consequences of oxidant generation in the lungs are unclear. In this study, we addressed the link between the H2O2-generating enzyme NADPH oxidase 4 (NOX4) and di-tyrosine (DT), an oxidative post-translational modification in IPF lungs. We performed immunohistochemical staining for DT and NOX4 in pulmonary tissue from patients with IPF and controls using validated antibodies. In the healthy lung, DT showed little or no staining and NOX4 was mostly present in normal vascular endothelium. On the other hand, both markers were detected in several cell types in the IPF patients, including vascular smooth muscle cells and epithelium (bronchial cells and epithelial cells type II). The link between NOX4 and DT was addressed in human fibroblasts deficient for NOX4 activity (mutation in the CYBA gene). Induction of NOX4 by Transforming growth factor beta 1 (TGFβ1) in fibroblasts led to moderate DT staining after the addition of a heme-containing peroxidase in control cells but not in the fibroblasts deficient for NOX4 activity. Our data indicate that DT is a histological marker of IPF and that NOX4 can generate a sufficient amount of H2O2 for DT formation in vitro.

Pro/Antioxidant State as a Potential Biomarker of Schizophrenia.

To allow better diagnosis and management of psychiatric illnesses, the use of easily accessible biomarkers are proposed. Therefore, recognition of some diseases by a set of related pathogenesis biomarkers is a promising approach. The study aims to assess the usefulness of examining oxidative stress (OS) in schizophrenia as a potential biomarker of illness using the commonly used data mining decision tree method. The study group was comprised of 147 participants: 98 patients with schizophrenia (SZ group), and the control group (n = 49; HC). The patients with schizophrenia were divided into two groups: first-episode schizophrenia (n = 49; FS) and chronic schizophrenia (n = 49; CS). The assessment included the following biomarkers in sera of patients: catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase-1 (SOD-1), glutathione reductase (GR), reduced glutathione (GSH), total antioxidant capacity (TAC), ferric reducing ability of plasma (FRAP), advanced glycation end products (AGEs), advanced oxidation protein products (AOPP), dityrosine (DITYR), kynurenine (KYN), N-formylkynurenine (NFK), tryptophan (TRY), total oxidant status (TOS), nitric oxide (NO) and total protein. Maximum accuracy (89.36%) for distinguishing SZ from HC was attained with TOS and GPx (cut-off points: 392.70 and 15.33). For differentiating between FS and CS, the most promising were KYN, AOPP, TAC and NO (100%; cut-off points: 721.20, 0.55, 64.76 and 2.59). To distinguish FS from HC, maximum accuracy was found for GSH and TOS (100%; cut-off points: 859.96 and 0.31), and in order to distinguish CS from HC, the most promising were GSH and TOS (100%; cut-off points: 0.26 and 343.28). Using redox biomarkers would be the most promising approach for discriminating patients with schizophrenia from healthy individuals and, in the future, could be used as an add-on marker to diagnose and/or respond to treatment.

Oxidative Stress Conditions Result in Trapping of PHF-Core Tau (297-391) Intermediates.

The self-assembly of tau into paired helical filaments (PHFs) in neurofibrillary tangles (NFTs) is a significant event in Alzheimer’s disease (AD) pathogenesis. Numerous post-translational modifications enhance or inhibit tau assembly into NFTs. Oxidative stress, which accompanies AD, induces multiple post-translational modifications in proteins, including the formation of dityrosine (DiY) cross-links. Previous studies have revealed that metal-catalysed oxidation (MCO) using Cu2+ and H2O2 leads to the formation of DiY cross-links in two misfolding proteins, Aβ and α-synuclein, associated with AD and Parkinson’s disease respectively. The effect of MCO on tau remains unknown. Here, we examined the effect of MCO and ultra-violet oxidation to study the influence of DiY cross-linking on the self-assembly of the PHF-core tau fragment. We report that DiY cross-linking facilitates tau assembly into tau oligomers that fail to bind thioflavin S, lack β-sheet structure and prevents their elongation into filaments. At a higher concentration, Cu2+ (without H2O2) also facilitates the formation of these tau oligomers. The DiY cross-linked tau oligomers do not cause cell death. Our findings suggest that DiY cross-linking of pre-assembled tau promotes the formation of soluble tau oligomers that show no acute impact on cell viability.

Noxious effects of selected food-occurring oxidized amino acids on differentiated CACO-2 intestinal human cells

The harmful effects of food-occurring oxidized amino acids, namely, aminoadipic acid (AAA), dityrosine (DTYR), L-kynurenine (KN), kynurenic acid (KA) and 3-nitrotyrosine (3NT), were studied on differentiated CACO-2 cells by flow cytometry and quantification of glutathione (GSH), and allysine. Cells were exposed to food-relevant doses (200 μM) of each compound for 4 or 72h and compared to a control (no stimulated cells). All oxidized amino acids induced apoptosis and results indicated that underlying mechanisms depended on the chemical nature of the species. AAA, KN and KA caused ROS generation and severe oxidative stress in 96%, 98% and 89% of exposed cells (77% in control cells), leading to significant GSH depletion and allysine accretion (1.5, 1.5 and 1.6 nmol allysine/mg protein, respectively at 4h; control: 0.22 nmol/mg protein; p < 0.05). DTYR and 3NT induced significant apoptosis to 29% and 25% of cells (control: 16%; p < 0.05) and necrosis to 28% and 26% of cells (control: 23%) at 72h by ROS-independent mechanisms. KN and KA were found to induce a cycle arrest effect on CACO-2 cells. These findings emphasize the potential harmful effects of the intake of oxidized proteins and amino acids and urge the necessity of carrying out further molecular studies.

Effects of a Forest Walk on Urinary Dityrosine and Hexanoyl-Lysine in Young People: A Pilot Study.

A few studies indicate exposure to forests may alleviate oxidative stress in the body. However, more evidence is needed to support this potentiality. The purpose of the current study aimed at examining whether there is any difference in urinary levels of oxidatively modified proteins or lipids—dityrosine (DT) and hexanoyl-lysine (HEL), respectively, after a forest or urban walk. The study was performed on 29 university students who took part in forest walks (Shinjo Village) in Okayama Prefecture of Japan and on 42 university students who took part in urban walks in the downtown area of Okayama City. Urine samples before and after the walks were analyzed for DT and HEL excretion. Air phytoncides during the walks were also measured. We found a decreased tendency in urinary DT and HEL (p < 0.05) in most participants after the forest walks, but not after the urban walks. We further found the total levels of air phytoncides in the forest field were 1.50 times higher compared with those in the urban field. This study suggests the possibility that regular immersion in a forest environment might contribute toward weakening of the oxidative modifications of proteins or lipids in the body.

Gold Nanoparticle as a Lewis Catalyst for Water Elimination of Tyrosine-•OH Adducts: A Radiation and Quantum Chemical Study.

The role of gold nanoparticles (AuNPs) in the degradation of tyrosine intermediates formed during the radiation-induced •OH reaction with tyrosine at pH 6.5 is investigated by measuring the radiolytic yields, G, of tyrosine (-Tyr), dityrosine (DT), and 3,4 dihydroxyphenylalanine (DOPA). The G(DT) is doubled, whereas G(-Tyr) calculated is halved in the presence of 6.0 × 10-10 mol dm-3 AuNPs. Pulse radiolysis studies are carried out to elucidate the mechanism and nature of the transient formed in the reaction of •OH and •N3 with tyrosine. The formation of tyrosyl radical in the presence of AuNPs is found to be a major pathway through the decay of tyrosine-•OH adducts via the water elimination reaction, which is found to be 3× faster in the presence of AuNPs. Quantum chemical calculations on the system showed favorable formation of the tyrosine-AuNP complex. A new plausible mechanism of tyrosine-AuNP complex acting as a Lewis type catalyst in the decay of tyrosine-•OH adducts leading to reduced DOPA formation is proposed. The proposed mechanism is also complemented by the electronic spectra and energetics of the reaction of •OH with tyrosine using density functional theory calculations. Significantly, the H-shift reaction of ortho-tyrosine-•OH adducts is also found to be energetically viable. The investigation provides a new physical insight into the effect of AuNPs on the decay of free-radical transient species and demonstrates the potential of radiation chemical techniques and quantum chemical calculations as a tool for understanding the impact of metal nanoparticles in free-radical oxidation of amino acids, which is important in the use of metal nanoparticles for biomedical applications.

Investigation of the effect of sodium nitrite on protein oxidation markers in food protein suspensions.

The aim of this study is to investigate the effect of sodium nitrite (NaNO2 ) on protein oxidation and the use of 3-nitrotyrosine (3NT) as a protein oxidation marker in suspensions of the food protein. Food proteins, namely bovine serum albumin, casein, and myofibrillar protein, were suspended in 100mM sodium phosphate buffer and nitrated with 25µM iron (III) chloride, 2.5mM hydrogen peroxide, and 150mg/kg NaNO2 at 37°C for a period of 24hr. The food protein suspensions were analyzed at different sampling periods for the loss of tryptophan (TRY) residues as well as the formation of Schiff bases (SBs), protein carbonyls, 3NT, and dityrosine (DT). It was found that NaNO2 has pro-oxidant activity in NaNO2 -added food protein suspensions due to the increased amounts of SBs, protein carbonyls, 3NT, and DT as well as decreased TRY fluorescence. Positive correlations between the 3NT and other protein oxidation markers except for TRY fluorescence were found in NaNO2 -added food protein suspensions. In conclusion, these findings on the detection of 3NT indicate that it might be a useful tool as a new protein oxidation biomarker in food samples. PRACTICAL APPLICATIONS: Sodium nitrite (NaNO2 ) supports protein oxidation in different food protein suspension. 3-nitrotyrosine (3NT) was found in food protein suspensions and can be a potential biomarker for protein nitration in food sample due to potential relationship between 3NT and other oxidation markers. The results showed that this study has formed novel insight into interaction between NaNO2 and food proteins and indicate that it might affect the food quality and its nutritional value. Moreover, the relationship between protein oxidation/nitration and food quality as well as the comprehension of the scientific and technological meaning of these phenomena has been hindered because of the lack of knowledge about the basic chemistry behind the protein oxidation and nitration pathways. For the clarification of these phenomena, further studies are still needed.

Genotypic variation for cadmium tolerance in common bean (Phaseolus vulgaris L.).

Given the limitation of crop production in Cd-polluted areas, the identification and selection of plant genotypes tolerant to Cd stress are of great significance. In the present work, we show the existence of genotypic variation for Cd tolerance in common bean. The laboratory screening of 25 bean genotypes indicated a significant positive correlation of the mean productivity (MP) and the geometric mean productivity (GMP) with plant fresh weight both in control and Cd-treated plants. A principal component analysis further confirmed this variation and, together with other analyses, led to the selection of genotypes G-11867, Taylor, Emerson, and D-81083 as tolerant genotypes. A total of six bean genotypes with different degrees of Cd tolerance were selected, and their long-term physiological responses to Cd (0, 45, and 90mg/kg soil) were evaluated. Increasing Cd concentrations led to higher Cd accumulation both in roots and shoots, and to significant rises in the levels of the oxidative stress biomarkers malondialdehyde (MDA), dityrosine (D-T), and 8-hydroxy-2'-deoxyguanosine (8-OH-2'-dG). Remarkable reductions in plant hormone levels and chlorophyll contents, as well as in dry and fresh weight, were observed in Cd-treated plants. Among the examined genotypes, Emerson, Taylor, and G-11867 were found to be more tolerant to Cd owing to lower Cd accumulation and lower oxidative stress levels, as well as higher chlorophyll and hormone contents. Our results contribute to the understanding of the physiological and biochemical basis of Cd tolerance in bean plants and may therefore, be useful for breeding programs directed towards obtaining bean varieties showing low Cd accumulation.

Spatial Learning and Memory Impairment in Growing Mice Induced by Major Oxidized Tyrosine Product Dityrosine.

This study focused on the effects of oxidized tyrosine products (OTPs) and major component dityrosine (DT) on the brain and behavior of growing mice. Male and female mice were treated with daily intragastric administration of either tyrosine (Tyr; 420 μg/kg body weight), DT (420 μg/kg body weight), or OTPs (1909 μg/kg body weight) for 35 days. We found that pure DT and OTPs caused redox state imbalance, elevated levels of inflammatory factors, hippocampal oxidative damage, and neurotransmitter disorders while activating the mitochondrial apoptosis pathway in the hippocampus and downregulating the genes associated with learning and memory. These events eventually led to growing mice learning and memory impairment, lagging responses, and anxiety-like behaviors. Furthermore, the male mice exhibited slightly more oxidative damage than the females. These findings imply that contemporary diets and food-processing strategies of the modern world should be modified to reduce oxidized protein intake.