Total low-molecular-weight antioxidants as a summary parameter, quantified in biological samples by a chemiluminescence inhibition assay

Donor-Dependent Variations in Systemic Oxidative Stress and Their Association with One-Year Graft Outcomes in Kidney Transplantation

INTRODUCTION

Oxidative stress has been implicated in complications after kidney transplantation (KT), including delayed graft function (DGF) and rejection. However, its role in long-term posttransplant outcomes remains unclear.

METHODS

We investigated oxidative damage and antioxidant defense dynamics, and their impact on the graft outcomes, in 41 KT recipients categorized by type of donation over 12 months. Oxidative status was determined using OxyScore and AntioxyScore indexes, which comprise several circulating biomarkers of oxidative damage and antioxidant defense. Donor types included donation after brain death (DBD [61.0%]), donation after circulatory death (DCD [26.8%]), and living donation (LD [12.1%]).

RESULTS

There was an overall increase in oxidative damage early after transplantation, which was significantly higher in DCD as compared to DBD and LD recipients. The multivariate adjustment confirmed the independent association of OxyScore and type of deceased donation with DGF, donor kidney function, and induction therapy with antithymocyte globulin. There were no differences in terms of antioxidant defense. Lower oxidative damage at day 7 predicted better graft function at 1-year posttransplant only in DBD recipients.

CONCLUSION

DCD induced greater short-term oxidative damage after KT, whereas the early levels of oxidative damage were predictive of the graft function 1 year after KT among DBD recipients.

Albumin Redox Modifications Promote Cell Calcification Reflecting the Impact of Oxidative Status on Aortic Valve Disease and Atherosclerosis

Calcific aortic valve disease (CAVD) and coronary artery disease (CAD) are related cardiovascular diseases in which common mechanisms lead to tissue calcification. Oxidative stress plays a key role in these diseases and there is also evidence that the redox state of serum albumin exerts a significant influence on these conditions. To further explore this issue, we used multimarker scores (OxyScore and AntioxyScore) to assess the global oxidative status in patients with CAVD, with and without CAD, also evaluating their plasma thiol levels. In addition, valvular interstitial cells were treated with reduced, oxidized, and native albumin to study how this protein and its modifications affect cell calcification. The differences we found suggest that oxidative status is distinct in CAVD and CAD, with differences in redox markers and thiol levels. Importantly, the in vitro interstitial cell model revealed that modified albumin affects cell calcification, accelerating this process. Hence, we show here the importance of the redox system in the development of CAVD, emphasizing the relevance of multimarker scores, while also offering evidence of how the redox state of albumin influences vascular calcification. These data highlight the relevance of understanding the overall redox processes involved in these diseases, opening the door to new studies on antioxidants as potential therapies for these patients.

Decoupling of the Confused Complex in Oxidation of 3,3',5,5'-Tetramethylbenzidine for the Reliable Chromogenic Bioassay

Regulation of the reaction pathways is a perennial theme in the field of chemistry. As a typical chromogenic substrate, 3,3',5,5'-tetramethylbenzidine (TMB) generally undertakes one-electron oxidation, but the product (TMBox1) is essentially a confused complex and is unstable, which significantly hampers the clinic chromogenic bioassays for more than 50 years. Herein, we report that sodium dodecyl sulfate (SDS)-based micelles could drive the direct two-electron oxidation of TMB to the final stable TMBox2. Rather than activation of H2O2 oxidant in the one-electron TMB oxidation by common natural peroxidase, activation of the TMB substrate by SDS micelles decoupled the thermodynamically favorable complex between TMBox2 with unreacted TMB, leading to an unusual direct two-electron oxidation pathway. Mechanism studies demonstrated that the complementary spatial and electrostatic isolation effects, caused by the confined hydrophobic cavities and negatively charged outer surfaces of SDS micelles, were crucial. Further cascading with glucose oxidase, as a proof-of-concept application, allowed glucose to be more reliably measured, even in a broader range of concentrations without any conventional strong acid termination.

A Comparative Study of the Inhibitory Effect of Some Flavonoids and a Conjugate of Taxifolin with Glyoxylic Acid on the Oxidative Burst of Neutrophils

During the storage, processing, and digestion of flavonoid-rich foods and beverages, a condensation of flavonoids with toxic carbonyl compounds occurs. The effect of the resulting products on cells remains largely unknown. The aim of the present study was to evaluate the effects of quercetin, taxifolin, catechin, eriodictyol, hesperetin, naringenin, and a condensation product of taxifolin with glyoxylic acid on the oxidative burst of neutrophils. It was found that the flavonoids and the condensation product inhibited the total production of ROS. Flavonoids decreased both the intra and extracellular ROS production. The condensation product had no effect on intracellular ROS production but effectively inhibited the extracellular production of ROS. Thus, the condensation of flavonoids with toxic carbonyl compounds may lead to the formation of compounds exhibiting potent inhibitory effects on the oxidative burst of neutrophils. The data also suggest that, during these reactions, the influence of a fraction of flavonoids and their polyphenolic derivatives on cellular functions may change. On the whole, the results of the study provide a better understanding of the effects of polyphenols on human health. In addition, these results reveal the structure-activity relationship of these polyphenols and may be useful in a search for new therapeutic agents against diseases associated with oxidative stress.

Global Oxidative Status Is Linked to Calcific Aortic Stenosis: The Differences Due to Diabetes Mellitus and the Effects of Metformin

Calcific aortic stenosis (CAS) and type 2 diabetes mellitus (T2DM) are related and often concomitant pathologies, accompanied by common comorbidities such as hypertension or dyslipidemia. Oxidative stress is one of the mechanisms that trigger CAS, and it can drive the vascular complications in T2DM. Metformin can inhibit oxidative stress, yet its effects have not been studied in the context of CAS. Here, we assessed the global oxidative status in plasma from patients with CAS, both alone and with T2DM (and under treatment with metformin), using multimarker scores of systemic oxidative damage (OxyScore) and antioxidant defense (AntioxyScore). The OxyScore was determined by measuring carbonyls, oxidized LDL (oxLDL), 8-hydroxy-20-deoxyguanosine (8-OHdG), and xanthine oxidase (XOD) activity. In contrast, the AntioxyScore was determined through the catalase (CAT) and superoxide dismutase (SOD) activity, as well as the total antioxidant capacity (TAC). Patients with CAS displayed enhanced oxidative stress compared to control subjects, probably exceeding their antioxidant capacity. Interestingly, patients with CAS and T2DM displayed less oxidative stress, possibly due to the benefits of their pharmacological therapy (metformin). Thus, reducing oxidative stress or enhancing antioxidant capacity through specific therapies could be a good strategy to manage CAS, focusing on personalized medicine.

Chemiluminescence Detection in the Study of Free-Radical Reactions. Part 1

The present review, consisting of two parts, considers the application of the chemiluminescence detection method in evaluating free radical reactions in biological model systems. The first part presents a classification of experimental biological model systems. Evidence favoring the use of chemiluminescence detection in the study of free radical reactions, along with similar methods of registering electromagnetic radiation as electron paramagnetic resonance, spectrophotometry, detection of infrared radiation (IR spectrometry), and chemical methods for assessing the end products of free radical reactions, is shown. Chemiluminescence accompanying free radical reactions involving lipids has been the extensively studied reaction. These reactions are one of the key causes of cell death by either apoptosis (activation of the cytochrome c complex with cardiolipin) or ferroptosis (induced by free ferrous ions). The concept of chemiluminescence quantum yield is also discussed in this article. The second part, which is to be published in the next issue, analyzes the application of chemiluminescence detection using luminescent additives that are called activators, a.k.a. chemiluminescence enhancers, and enhance the emission through the triplet-singlet transfer of electron excitation energy from radical reaction products, followed by light emission with a high quantum yield.

Analysis of Global Oxidative Status Using Multimarker Scores Reveals a Specific Association Between Renal Dysfunction and Diuretic Therapy in Older Adults

Aging and chronic kidney disease (CKD) are important interrelated cardiovascular risk (CVR) factors linked to oxidative stress, but this relationship has not been well studied in older adults. We assessed the global oxidative status in an older population with normal to severely impaired renal function. We determined the oxidative status of 93 older adults (mean age 85 years) using multimarker scores. OxyScore was computed as index of systemic oxidative damage by analyzing carbonyl groups, oxidized low-density lipoprotein, 8-hydroxy-2'-deoxyguanosine, and xanthine oxidase activity. AntioxyScore was computed as index of antioxidant defense by analyzing catalase and superoxide dismutase (SOD) activity and total antioxidant capacity. OxyScore and AntioxyScore were higher in subjects with estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 than in peers with eGFR >60 mL/min/1.73 m2, with protein carbonyls, catalase, and SOD activity as major drivers. Older adults with a recent cardiovascular event had similar OxyScore and AntioxyScore as peers with eGFR >60 mL/min/1.73 m2. Multivariate linear regression analysis revealed that both indices were associated with decreased eGFR independently of traditional CVR factors. Interestingly, AntioxyScore was also associated with diuretic treatment, and a more pronounced increase was seen in subjects receiving combination therapy. The associations of AntioxyScore with diuretic treatment and eGFR were mutually independent. In conclusion, eGFR is the major contributor to the imbalance in oxidative stress in this older population. Given the association between oxidative stress, CKD, and CVR, the inclusion of renal function parameters in CVR estimators for older populations, such as the SCORE-OP, might improve their modest performance.

Early Posttransplant Mobilization of Monocytic Myeloid-derived Suppressor Cell Correlates With Increase in Soluble Immunosuppressive Factors and Predicts Cancer in Kidney Recipients

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) increase in patients with cancer and are associated with poor prognosis; however, their role in transplantation is not yet understood. Here we aimed to study the MDSC effects on the evolution of kidney transplant recipients (KTRs).

METHODS

A cohort of 229 KTRs was prospectively analyzed. Two myeloid cells subsets. CD11bCD33CD14CD15HLA-DR (monocytic MDSC [M-MDSC]) and CD11bCD33CD14CD15HLA-DR (monocytes), were defined by flow cytometry. The suppressive capacity of myeloid cells was tested in cocultures with autologous lymphocytes. Suppressive soluble factors, cytokines, anti-HLA antibodies, and total antioxidant capacity were quantified in plasma.

RESULTS

Pretransplant, M-MDSC, and monocytes were similar in KTRs and healthy volunteers. M-MDSCs increased immediately posttransplantation and suppressed CD4 and CD8 T cells proliferation. M-MDSCs remained high for 1 y posttransplantation. Higher M-MDSC counts at day 14 posttransplant were observed in patients who subsequently developed cancer, and KTRs with higher M-MDSC at day 14 had significantly lower malignancy-free survival. Day 14 M-MDSC >179.2 per microliter conferred 6.98 times (95% confidence interval, 1.28-37.69) more risk to develop cancer, independently from age, gender, and immunosuppression. Early posttransplant M-MDSCs were lower in patients with enhanced alloimmune response as represented by anti-HLA sensitization. M-MDSC counts correlated with higher circulatory suppressive factors arginase-1 and interleukin-10, and lower total antioxidant capacity.

CONCLUSIONS

Early posttransplant mobilization of M-MDSCs predicts cancer and adds risk as an independent factor. M-MDSC may favor an immunosuppressive environment that promotes tumoral development.

Oxidative Status before and after Renal Replacement Therapy: Differences between Conventional High Flux Hemodialysis and on-Line Hemodiafiltration

Hemodialysis patients experience high oxidative stress because of systemic inflammation and depletion of antioxidants. Little is known about the global oxidative status during dialysis or whether it is linked to the type of dialysis. We investigated the oxidative status before (pre-) and after (post-) one dialysis session in patients subjected to high-flux dialysis (HFD) or on-line hemodiafiltration (OL-HDF). We analyzed carbonyls, oxidized LDL (oxLDL), 8-hydroxy-2′-deoxyguanosine, and xanthine oxidase (XOD) activity as oxidative markers, and total antioxidant capacity (TAC), catalase, and superoxide dismutase activities as measures of antioxidant defense. Indices of oxidative damage (OxyScore) and antioxidant defense (AntioxyScore) were computed and combined into a global DialysisOxyScore. Both dialysis modalities cleared all markers (p < 0.01) except carbonyls, which were unchanged, and oxLDL, which increased post-dialysis (p < 0.01). OxyScore increased post-dialysis (p < 0.001), whereas AntioxyScore decreased (p < 0.001). XOD and catalase activities decreased post-dialysis after OL-HDF (p < 0.01), and catalase activity was higher after OL-HDF than after HFD (p < 0.05). TAC decreased in both dialysis modalities (p < 0.01), but remained higher in OL-HDF than in HFD post-dialysis (p < 0.05), resulting in a lower overall DialysisOxyScore (p < 0.05). Thus, patients on OL-HDF maintain higher levels of antioxidant defense, which might balance the elevated oxidative stress during dialysis, although further longitudinal studies are needed.

Lifetime cardiovascular risk is associated with a multimarker score of systemic oxidative status in young adults independently of traditional risk factors

Cardiovascular risk (CVR) tends to be estimated in the short-term, which underestimates lifetime (LT)-CVR of young subjects. We determined whether LT-CVR is associated with a multimarker score of oxidative status in young adults and whether this association is independent of traditional CVR factors. Seventy-two young adults were stratified into: (1) low or (2) high LT-CVR, and (3) stable coronary artery disease (SCAD). CVR was estimated with QRisk and atherosclerotic CV disease (ASCVD) risk estimators, or second manifestations of arterial disease (SMART). Risk score. oxidative damage was determined by measuring carbonyls, oxidized LDL (oxLDL), 8-hydroxy-2'-deoxyguanosine (8-OHdG), and xanthine oxidase activity. Antioxidant defence was determined by total antioxidant capacity (TAC), catalase (CAT) activity and superoxide dismutase (SOD) activity. Multimarker scores of systemic oxidative damage (OxyScore) and antioxidant defence (AntioxyScore) were computed as standardized variables. Subjects with high LT-CVR had significantly higher levels of oxLDL, 8-OHdG, TAC, and CAT activity than subjects with low LT-CVR or with SCAD. QRisk and ASCVD estimators correlated positively with oxLDL, TAC, and CAT activity, while SMART Risk Score correlated with carbonyls and SOD activity. OxyScore and AntioxyScore were significantly higher in subjects with high LT-CVR than with low LT-CVR or with SCAD. OxyScore, but not AntioxyScore, was associated with LT-CVR independently of each traditional CVR factor. This study for the first time demonstrates a positive association between oxidative stress and the risk of first and recurrent CV events in young adults.

Redox Modulators Determine Luminol Luminescence Generated by Porphyrin-Coordinated Iron and May Repress "Suicide Inactivation"

Iron porphyrin catalysts of the luminol reaction (horseradish peroxidase, hemoglobin, cytochrome c, and hemin) interact with diverse reducing compounds. Here, it is demonstrated how the chemiluminescence yield is modulated by such interactions. The compounds accepted as substrates protect the catalyst against the "suicide inactivation" caused by high peroxide concentrations. The reducing agents not accepted by the catalyst inhibit light production either by generating a futile redox cycle of the luminophore or by irreversibly inactivating the catalytic center. In the case of a futile cycle, light emission resumes as soon as the reducing agents in the reaction are consumed, whereas with an irreversible inactivation, light emission does not recover. The characteristics of luminescence enhancement and quenching depending on interfering agents are also reported here. They reveal details about the relative redox potentials of the involved compounds. It is discussed how this should be considered when the luminol reaction is used for quantitative analyses and when unpurified samples with a broad compound matrix are to be assayed.

Maternal plasma antioxidant status in the first trimester of pregnancy and development of obstetric complications

INTRODUCTION

Oxidative stress is present in pregnancy complications. However, it is unknown if early maternal antioxidant status could influence later development of complications. The use of assisted reproduction techniques (ART) is rising due to the delay of first pregnancy and there is scarce information on its influence on oxidative balance.

OBJECTIVE

To assess the possible relationship between maternal plasma antioxidant status in first trimester of gestation with later development of pregnancy complications, evaluating the influence of ART and nutrition.

METHODS

Plasma from 98 healthy pregnant women was obtained at week 10, nutrition questionnaires filled and women were followed until delivery. We evaluated biomarkers of oxidative damage (carbonyls, malondialdehyde-MDA), antioxidants (thiols, reduced glutathione, phenolic compounds, catalase and superoxide dismutase activities) by spectrophotometry/fluorimetry and melatonin (ELISA). Antioxidant status score (Antiox-S) was calculated as the computation of antioxidants. Diet-antioxidants relationship was evaluated through multiple correspondence analysis.

RESULTS

Melatonin and carbonyls exhibited a negative correlation. No difference in oxidative damage was found between groups, but Antiox-S was significantly lower in women who developed complications. No differences in oxidative damage or Antiox-S were found between ART and no-ART pregnancies. High consumption of foods of vegetable origin cluster with high plasma levels of phenolic compounds and with high Antiox-S.

CONCLUSIONS

In early normal gestation, low plasma antioxidant status, assessed through a global score, associates with later development of pregnancy complications. Larger population studies could help to determine the value of Antiox-S as predictive tool and the relevance of nutrition on maternal antioxidant status.

Development of albuminuria and enhancement of oxidative stress during chronic renin-angiotensin system suppression

OBJECTIVE

Albuminuria has been recently described in hypertensive patients under chronic renin-angiotensin system (RAS) suppression. We investigated whether this fact could be related to an increase in oxidative stress.

METHODS

We examined normoalbuminuric and albuminuric patients in stage 2 chronic kidney disease, both with more than 2 years of RAS blockade. The relationship between albuminuria and circulating biomarkers for both oxidative damage, that is carbonyl and malondialdehyde, as well as antioxidant defense, that is reduced glutathione, thiol groups, uric acid, bilirubin, or catalase, and superoxide scavenging activity, was assessed.

RESULTS

We found that only patients with albuminuria showed an important increase in carbonyls (P < 0.001) and malondialdehyde (P < 0.05) compared to normoalbuminuric patients. This increase in oxidative damage was also accompanied by a rise in catalase activity (P < 0.05) and low-molecular-weight antioxidants only when they were measured as total antioxidant capacity (P < 0.01). In order to establish the specific oxidative status of each group, new indexes of oxidative damage and antioxidant defense were calculated with all these markers following a mathematical and statistical approach. Although both pro-oxidant and antioxidant indexes were significantly increased in patients with albuminuria, only the oxidative damage index positively correlated with the increase of albumin/creatinine ratio (P = 0.0024).

CONCLUSIONS

We conclude that albuminuria is accompanied by an amplified oxidative damage in patients in early stages of chronic kidney disease. These results indicate that chronic RAS protection must be directed to avoid development of albuminuria and oxidative damage.

Concurrent measurement of cellular turbidity and hemoglobin to evaluate the antioxidant activity of plants

In past decades, a multitude of analytical methods for measuring antioxidant activity of plant extracts has been developed. However, when using methods to determine hemoglobin released from human erythrocytes treated with ginger extracts, we found hemoglobin concentrations were significantly higher than in untreated control samples. This suggests in the presence of antioxidants that measuring hemoglobin alone is not sufficient to determine hemolysis. We show concurrent measurement of erythrocyte concentration and hemoglobin is essential in such assays, and describe a new protocol based on simultaneous measurement of cellular turbidity and hemoglobin.

Decorating PtCo bimetallic alloy nanoparticles on graphene as sensors for glucose detection by catalyzing luminol chemiluminescence

A new type of PtCo(x) @graphene nanocomposite is prepared by a simple chemical solution method, which can dramatically enhance the chemiluminescence (CL) intensity of luminol-H(2)O(2) system, making it possible for the detection of glucose through measuring the H(2)O(2) produced from its catalytic oxidation.

A plasma oxidative stress global index in early stages of chronic venous insufficiency

BACKGROUND

Chronic venous insufficiency (CVI) represents a social and health care problem because it affects working age populations, particularly in jobs requiring orthostasis, has no effective pharmacologic treatment, and requires surgery. Oxidative stress is present in varicose veins, but whether this is reflected in the plasma is controversial. We aimed to quantify plasma oxidative stress biomarkers in the early stages of CVI and calculate a global index of oxidative stress representative of the disease.

METHODS

Plasma was obtained from blood samples of nine patients with CEAP C2 stage CVI and 10 healthy controls. Biomarkers related to antioxidant defense systems (total thiols, reduced glutathione, uric acid, total antioxidant capacity, catalase), oxidative damage (malondialdehyde-bound protein, protein carbonyls, advanced oxidation products, and 3-nitrotyrosine), and activity of enzymes producing key free radicals (xanthine oxidase and myeloperoxidase) were assessed.

RESULTS

Compared with the controls, CVI patients exhibited decreased catalase activity and thiol levels and increased malondialdehyde-bound protein and protein carbonyls. These parameters were used to calculate the global index of oxidative stress in CVI, which was significantly different between groups.

CONCLUSIONS

It is possible to detect significant changes in plasma oxidative stress biomarkers in early stages of CVI and to calculate a global index representative of the oxidative status in an individual. This index, with the appropriate validation in a larger population, could be used for early detection or progression of CVI.

Unprecedented hydroxyl radical-dependent two-step chemiluminescence production by polyhalogenated quinoid carcinogens and H2O2

Most chemiluminescence (CL) reactions usually generate only one-step CL, which is rarely dependent on the highly reactive and biologically/environmentally important hydroxyl radicals ((•)OH). Here, we show that an unprecedented two-step CL can be produced by the carcinogenic tetrachloro-1,4-benzoquinone (also known as p-chloranil) and H(2)O(2), which was found to be well-correlated to and directly dependent on its two-step metal-independent production of (•)OH. We proposed that (•)OH-dependent formation of quinone-dioxetane and electronically excited carbonyl species might be responsible for this unusual two-step CL production by tetrachloro-1,4-benzoquinone/H(2)O(2). This is a unique report of a previously undefined two-step CL-producing system that is dependent on intrinsically formed (•)OH. These findings may have potential applications in detecting and quantifying (•)OH and the ubiquitous polyhalogenated aromatic carcinogens, which may have broad biological and environmental implications for future research on these types of important species.

Determination of oxidative stress in wheat leaves as influenced by boron toxicity and NaCl stress

Boron (B) toxicity symptoms are visible in the form of necrotic spots and may worsen the oxidative stress caused by salinity. Hence, the interactive effects of combined salinity and B toxicity stress on antioxidative activities (TAC, LUPO, SOSA, CAT, and GR) were investigated by novel luminescence assays and standard photometric procedures. Wheat plants grown under hydroponic conditions were treated with 2.5 μM H₃BO₃ (control), 75 mM NaCl, 200 μM H₃BO₃, or 75 mM NaCl + 200 μM H₃BO₃, and analysed 6 weeks after germination. Shoot fresh weight (FW), shoot dry weight (DW), and relative water content (RWC) were significantly reduced, whereas the antioxidative activity of all enzymes was increased under salinity compared with the control. High B application led to necrotic leaf spots but did not influence growth parameters. Following NaCl + B treatment, shoot DW, RWC, SOSA, GR, and CAT activities remained the same compared with NaCl alone, whereas the TAC and LUPO activities were increased under the combined stress compared with NaCl alone. However, shoot FW was significantly reduced under NaCl + B compared with NaCl alone, as an additive effect of combined stress. Thus, we found an adjustment of antioxidative enzyme activity to the interactive effects of NaCl and high B. The stress factor "salt" mainly produced more oxidative stress than that of the factor "high B". Furthermore, addition of higher B in the presence of NaCl increases TAC and LUPO demonstrating that increased LUPO activity is an important physiological response in wheat plants against multiple stresses.