Environmental risk factors and their footprints in vivo - A proposal for the classification of oxidative stress biomarkers

Effects of Baduanjin exercise on cognitive frailty, oxidative stress, and chronic inflammation in older adults with cognitive frailty: a randomized controlled trial

Background

Oxidative stress and chronic inflammation play an important role in the pathogenesis process of cognitive frailty (CF). Regular Baduanjin exercise could improve cognitive frailty in older adults, but it is unclear whether the effect of Baduanjin exercise on improving CF is mediated by modulating circulating oxidative stress and inflammatory process.

Method

A total of 102 community-dwelling older adults with CF were recruited and randomly allocated into a 24-week Baduanjin exercise training group or no specific exercise intervention control group at an equal rate. Cognitive function and physical frailty index were assessed using the Montreal Cognitive Assessment (MoCA) and the Edmonton Frail Scale (EFS), as well as the oxidative stress and inflammatory cytokines were measured at baseline and after intervention.

Result

After 24 weeks of intervention, the increased MoCA score (2.51 ± 0.32 points, p < 0.001) and the decreased EFS scores (1.94 ± 0.20 points, p = 0.012) in the Baduanjin group were significantly higher than those in the control group. Serum antioxidant SOD levels were increased by 10.03 ± 4.73 U/mL (p < 0.001), and the prooxidative MDA and 8-iso-PGF2α levels were decreased by -1.08 ± 0.80 nmol/mL (p = 0.030) and -86.61 ± 15.03 ng/L (p < 0.001) in the Baduanjin training group; while inflammatory cytokines IFN-γ, IL-2 and IL-4 levels were increased (1.08 ± 0.33 pg./mL, p = 0.034, 2.74 ± 0.75 pg./mL, p = 0.04 and 1.48 ± 0.35 pg./mL, p = 0.042). In addition, a mediation effect that Baduanjin training improved cognitive ability mediated by an increase of circulating IFN-γ and IL-2 levels were observed in this study.

Conclusion

Regular Baduanjin exercise training could improve the cognitive frailty of the community-dwelling older adults with CF, and modulate oxidative stress and inflammatory processes by reducing circulating pro-oxidative MDA and 8-iso-PGF2α levels and increasing anti-oxidative SOD levels, as well as impacting inflammatory cytokines IFN-γ, IL-2, and IL-4 levels. Nevertheless, the mechanism of Baduanjin exercise mediating oxidative stress and inflammatory processes should be cautious to be explained.

Clinical trial registration

http://www.chictr.org.cn/index.aspx, ChiCTR1800020341.

Tracing toxic path of antimony: From bioaccumulation to DNA hypomethylation in zebrafish (Danio rerio)

The increasing concentration of Antimony (Sb) in ecological environments has raised serious concerns about its potential biotoxicological impact. This study investigated the toxicokinetics, Global DNA Methylation (GDM), biomarker expression, and Integrated Biological Response (IBR) of Sb at different concentrations in zebrafish. The toxic mechanism of Sb exposure was simulated using molecular dynamics (MD). The results showed that significant differences effect existed (BCFk: liver > ovary > gut > brain) and uptake saturation phenomenon of Sb among zebrafish tissues. Over a 54-day exposure period, the liver emerged as the main target site for Sb-induced GDM, and the restoration was slower than in other tissues during the 54-day recovery period. Moreover, the concentration of Sb had a significant impact on the normally expression of biomarkers, with GSTM1 inhibited and MTF2, MT1, TET3, and p53 showing varying degrees of activation at different Sb concentrations. This could be attributed to Sb3+ potentially occupying the active site or tightly binding to the deep cavity of these genes. The IBR and MD results highlighted DNMT1 as the most sensitive biomarker among those assessed. This heightened sensitivity can be attributed to the stable binding of Sb3+ to DNMT1, resulting in alterations in the conformation of DNMT1's catalytic domain and inhibition of its activity. Consequently, this disruption leads to damage to the integrity of GDM. The study suggests that DNA methylation could serve as a valuable biomarker for assessing the ecotoxicological impact of Sb exposure. It contributes to a better understanding of the toxicity mechanisms in aquatic environments caused potential pollutants.

Efficacy of natural products on premature ovarian failure: a systematic review and meta-analysis of preclinical studies

OBJECTIVE

This study aims to investigate the effects of natural products on animal models of premature ovarian failure (POF).

METHODS

We conducted comprehensive literature searches and identified relevant studies that examined the protective effects of natural products on experimental POF. We extracted quantitative data on various aspects such as follicular development, ovarian function, physical indicators, oxidative stress markers, inflammatory factors, and protein changes. The data was analyzed using random-effects meta-analyses, calculating pooled standardized mean differences and 95% confidence intervals. Heterogeneity was assessed using the I2 statistic, and bias was estimated using the SYRCLE tool.

RESULTS

Among the 879 reviewed records, 25 articles met our inclusion criteria. These findings demonstrate that treatment with different phytochemicals and marine natural products (flavonoids, phenols, peptides, and alkaloids, etc.) significantly improved various aspects of ovarian function compared to control groups. The treatment led to an increase in follicle count at different stages, elevated levels of key hormones, and a decrease in atretic follicles and hormone levels associated with POF. This therapy also reduced oxidative stress (specifically polyphenols, resveratrol) and apoptotic cell death (particularly flavonoids, chrysin) in ovarian granulosa cells, although it showed no significant impact on inflammatory responses. The certainty of evidence supporting these findings ranged from low to moderate.

CONCLUSIONS

Phytochemicals and marine natural product therapy (explicitly flavonoids, phenols, peptides, and alkaloids) has shown potential in enhancing folliculogenesis and improving ovarian function in animal models of POF. These findings provide promising strategies to protect ovarian reserve and reproductive health. Targeting oxidative stress and apoptosis pathways may be the underlying mechanism.

Health position paper and redox perspectives - Disease burden by transportation noise

Transportation noise is a ubiquitous urban exposure. In 2018, the World Health Organization concluded that chronic exposure to road traffic noise is a risk factor for ischemic heart disease. In contrast, they concluded that the quality of evidence for a link to other diseases was very low to moderate. Since then, several studies on the impact of noise on various diseases have been published. Also, studies investigating the mechanistic pathways underlying noise-induced health effects are emerging. We review the current evidence regarding effects of noise on health and the related disease-mechanisms. Several high-quality cohort studies consistently found road traffic noise to be associated with a higher risk of ischemic heart disease, heart failure, diabetes, and all-cause mortality. Furthermore, recent studies have indicated that road traffic and railway noise may increase the risk of diseases not commonly investigated in an environmental noise context, including breast cancer, dementia, and tinnitus. The harmful effects of noise are related to activation of a physiological stress response and nighttime sleep disturbance. Oxidative stress and inflammation downstream of stress hormone signaling and dysregulated circadian rhythms are identified as major disease-relevant pathomechanistic drivers. We discuss the role of reactive oxygen species and present results from antioxidant interventions. Lastly, we provide an overview of oxidative stress markers and adverse redox processes reported for noise-exposed animals and humans. This position paper summarizes all available epidemiological, clinical, and preclinical evidence of transportation noise as an important environmental risk factor for public health and discusses its implications on the population level.

Effects of green tea polyphenols against metal-induced genotoxic damage: underlying mechanistic pathways

This review is based upon evidence from the published effects of green tea polyphenols (GTP) on genotoxic damage induced by metals with carcinogenic potential. First, the relationship between GTP and antioxidant defense system is provided. Subsequently, the processes involved in the oxidative stress generated by metals and their relationship to oxidative DNA damage is examined. The review demonstrated that GTP generally decrease oxidative DNA damage induced by exposure to metals such as arsenic (As), cadmium (Cd), cobalt (Co), copper (Cu), chromium (Cr), iron (Fe), and lead (Pb). The pathways involved in these effects are related to: (1) direct scavenging of free radicals (FR); (2) activation of mechanisms to repair oxidative DNA damage; (3) regulation of the endogenous antioxidant system; and (4) elimination of cells with genetic damage via apoptosis. The results obtained in the studies reviewed demonstrate potential for possible use of GTP to prevent and treat oxidative damage in populations exposed to metals. Further, GTP may be considered as adjuvants to treatments for metal-associated diseases related to oxidative stress and DNA damage.

Chrono-modulated effects of external stressors on oxidative stress and damage in humans: A scoping review on night shift work

BACKGROUND

Oxidative stress and tissue damage (OSD) play a pivotal role as an early-stage process in chronic disease pathogenesis. However, there has been little research to better understand the temporal (χρόνος[chronos]) dimensions of OSD process associated with environmental (non-genetic, including behaviors/lifestyle) and/or occupational stressors, like night shift work. OSD processes have recently attracted attention in relation to time-resolved external stressor trajectories in personalized medicine (prevention) initiatives, as they seem to interact with circadian clock systems towards the improved delineation of the early stages of (chronic) disease process.

OBJECTIVES

This work critically reviewed human studies targeting the temporal dynamics of OSD and circadian clock system's activity in response to environmental/occupational stressors; the case of night shift work was examined.

METHODS

Being a key stressor influencing OSD processes and circadian rhythm, night shift work was evaluated as part of a scoping review of research in OSD, including inflammatory and metabolic processes to determine the extent of OSD research undertaken in human populations, methodologies, tools and biomarkers used and the extent that the temporal dimensions of exposure and biological effect(s) were accounted for. Online databases were searched for papers published from 2000 onwards, resulting in the selection of 53 original publications.

RESULTS AND DISCUSSION

The majority of studies (n = 41) took place in occupational settings, while the rest were conducted in the general population or patient groups. Most occupational studies targeted outcomes of oxidative stress/damage (n = 19), followed by the combination of OSD with inflammatory response (n = 10), and studies focused on metabolic outcomes (n = 12). Only a minor fraction of the studies measured biomarkers related to circadian rhythm, such as, melatonin, its metabolite, or cortisol. Night shift work was associated with select biomarkers of OSD and inflammation, albeit with mixed results. Although much progress in delineating the biological mechanisms of OSD process has been made, an equally thorough investigation on the temporal trajectory of OSD processes as triggered by environmental/occupational stressors in human studies has yet to fully evolve.

Novel Oxidative Stress Biomarkers with Risk Prognosis Values in Heart Failure

Oxidative stress (OS) is mediated by reactive oxygen species (ROS), which in cardiovascular and other disease states, damage DNA, lipids, proteins, other cellular and extra-cellular components. OS is both initiated by, and triggers inflammation, cardiomyocyte apoptosis, matrix remodeling, myocardial fibrosis, and neurohumoral activation. These have been linked to the development of heart failure (HF). Circulating biomarkers generated by OS offer potential utility in patient management and therapeutic targeting. Novel OS-related biomarkers such as NADPH oxidases (sNox2-dp, Nrf2), advanced glycation end-products (AGE), and myeloperoxidase (MPO), are signaling molecules reflecting pathobiological changes in HF. This review aims to evaluate current OS-related biomarkers and their associations with clinical outcomes and to highlight those with greatest promise in diagnosis, risk stratification and therapeutic targeting in HF.

Is dietary intake of antioxidant vitamins associated with reduced adverse effects of air pollution on diabetes? Findings from a large cohort study

INTRODUCTION

It remains unknown whether higher dietary intake of antioxidant vitamins could reduce the harmful effects of air pollution on incident diabetes mellitus.

METHODS

A total of 156,490 participants free of diabetes mellitus in the UK Biobank data were included in this analysis. Antioxidant vitamin intake was measured using a 24-h food intake questionnaire, and results were categorized as sufficient or insufficient according to the British Recommended Nutrient Intake. Exposure to fine particles (PM_2.5), thoracic particles (PM₁₀), nitrogen dioxide (NO₂), and nitrogen oxide (NO_x) was estimated using land use regression models at participants' residences. Incident diabetes mellitus was identified using health administrative datasets. Cox regression models were used to assess the associations.

RESULTS

A total of 4271 incident diabetes mellitus cases were identified during a median follow-up of 11.7 years. Compared with participants with insufficient intake of antioxidant vitamins, those with sufficient consumption had a weaker association between air pollution (PM_2.5, PM₁₀ and NO₂) and diabetes mellitus [sufficient vs. insufficient: HR = 1.12 (95 % CI: 0.87, 1.45) vs. 1.69 (95 % CI: 1.42, 2.02) for PM_2.5, 1.00 (95 % CI: 0.88, 1.14) vs. 1.21 (95 % CI: 1.10, 1.34) for PM₁₀, and 1.01 (95 % CI: 0.98, 1.04) vs. 1.05 (95 % CI: 1.03, 1.07) for NO₂ (all p for comparison < 0.05)]. Among different antioxidant vitamins, we observed stronger effects for vitamin C and E.

CONCLUSION

Our study suggests that ambient air pollution is one important risk factor of diabetes mellitus, and sufficient intake of antioxidant vitamins may reduce such adverse effects of air pollution on diabetes mellitus.

Circulating metals, leukocyte microRNAs and microRNA networks: A profiling and functional analysis in Chinese adults

BACKGROUND

Metals in the human body represent both environmental exposure and nutritional status. Little is known about the miRNA signature in relation to circulating metals in humans.

OBJECTIVES

To characterize metal-associated miRNAs in leukocytes, individually and collectively as networks.

METHODS

In a panel of 160 Chinese adults, we measured 23 metals/metalloids in plasma, and sequenced miRNAs and mRNAs in leukocytes. We used linear regression to model the associations between ln-transformed metal concentrations and normalized miRNA levels adjusting for potential confounders. We inferred the enriched leukocyte subtypes for the identified miRNAs using an association approach. We utilized mRNA sequencing data to explore miRNA functions. We also constructed modules to identify metal-associated miRNA networks.

RESULTS

We identified 55 metal-associated miRNAs at false discovery rate-adjusted P < 0.05. In particular, we found that lead, nickel, and vanadium were positively associated with potentially lymphocyte-enriched miR-142-3p, miR-150-3p, miR-28-5p, miR-361-3p, and miR-769-5p, and were inversely associated with potentially granulocyte-enriched let-7a/c/d-5p and miR-1294. Interestingly, the five lymphocyte-enriched miRNAs inhibited, whereas miR-1294 activated, ROS and DNA repair pathways. We further confirmed the findings using oxidative damage biomarkers. Next, we clustered co-expressed miRNAs into modules, and identified four miRNA modules that were associated with different metals. The identified modules represented miRNAs enriched in different leukocyte subtypes, and were involved in biological processes including hematopoiesis and immune response, mitochondrial functions, and response to the stimulus.

CONCLUSIONS

At commonly exposed low levels, circulating metals were associated with distinct miRNA signatures in leukocytes. The identified miRNAs, individually or as regulatory networks, may provide a mechanistic link between metal exposure and pathophysiological changes in the immune system.

ConSIG: consistent discovery of molecular signature from OMIC data

The discovery of proper molecular signature from OMIC data is indispensable for determining biological state, physiological condition, disease etiology, and therapeutic response. However, the identified signature is reported to be highly inconsistent, and there is little overlap among the signatures identified from different biological datasets. Such inconsistency raises doubts about the reliability of reported signatures and significantly hampers its biological and clinical applications. Herein, an online tool, ConSIG, was constructed to realize consistent discovery of gene/protein signature from any uploaded transcriptomic/proteomic data. This tool is unique in a) integrating a novel strategy capable of significantly enhancing the consistency of signature discovery, b) determining the optimal signature by collective assessment, and c) confirming the biological relevance by enriching the disease/gene ontology. With the increasingly accumulated concerns about signature consistency and biological relevance, this online tool is expected to be used as an essential complement to other existing tools for OMIC-based signature discovery. ConSIG is freely accessible to all users without login requirement at https://idrblab.org/consig/.

Effects of exposure to environmental pollutants on mitochondrial DNA copy number: a meta-analysis

Exposure to environmental pollutants has been associated with alteration on relative levels of mitochondrial DNA copy number (mtDNAcn). However, the results obtained from epidemiological studies are inconsistent. This meta-analysis aimed to evaluate whether environmental pollutant exposure can modify the relative levels of mtDNAcn in humans. We performed a literature search using PubMed, Scopus, and Web of Science databases. We selected and reviewed original articles performed in humans that analyzed the relationship between environmental pollutant exposure and the relative levels of mtDNAcn; the selection of the included studies was based on inclusion and exclusion criteria. Only twenty-two studies fulfilled our inclusion criteria. A total of 6011 study participants were included in this systematic review and meta-analysis. We grouped the included studies into four main categories according to the type of environmental pollutant: (1) heavy metals, (2) polycyclic aromatic hydrocarbons (PAHs), (3) particulate matter (PM), and (4) cigarette smoking. Inconclusive results were observed in all categories; the pooled analysis shows a marginal increase of relative levels of mtDNAcn in response to environmental pollutant exposure. The trial sequential analysis and rate confidence in body evidence showed the need to perform new studies. Therefore, a large-scale cohort and mechanistic studies in this area are required to probe the possible use of relative levels of mtDNAcn as biomarkers linked to environmental pollution exposure.

Defining the Exposome Using Popular Education and Concept Mapping With Communities in Atlanta, Georgia

Introduction

The exposome concept provides a framework to better incorporate the environment into the study of health and disease and has been defined by academics to encompass all lifetime exposures including toxicants, diet, and lifestyle choices. However, initial applications of the exposome concept have been less apt at measuring social determinants of health, focusing primarily on conventional environmental exposures and lifestyle choices that do not reflect the complex lived experience of many communities. To bring community voice into the exposome concept, the HERCULES Exposome Research Center and its Stakeholder Advisory Board co-developed the Exposome Roadshow. We present and discuss the resulting community-exposome definition to inform and improve exposome research.

Materials and Methods

Four communities from distinct areas across metro-Atlanta participated in separate 2-day Exposome Roadshow workshops with concept mapping. Aligned with a popular education approach in which community knowledge is used to work collectively for change, concept mapping provided a systematic method to collect and visualize community members' knowledge and create a shared understanding to take action. Community members brainstormed, sorted, and rated their responses to the prompt: "What in your environment is affecting your and your community's health?" Responses were analyzed and visually depicted by concept maps consisting of separate but interrelated clusters of ideas. Community members discussed and validated the maps, selecting a final map illustrating their community's exposome.

Results

A total of 118 community members completed concept mapping. On average communities identified 7 clusters to define their exposome. The resulting concept maps offer a community definition of the exposome. Five major themes arose across all four communities: conventional environmental concerns, built environment, social relationships, crime and safety, and individual health and behaviors.

Discussion

The resulting community-exposome definition demonstrates the importance of expanding the scope of exposures beyond traditional environmental influences to include the lived experience of individuals and communities. While newer exposome definitions align more closely with this community definition, traditional exposome methods do not routinely include these factors. To truly capture the totality of lifetime exposures and improve human health, researchers should incorporate community perspectives into exposome research.

Bushen Culuan Decoction Ameliorates Premature Ovarian Insufficiency by Acting on the Nrf2/ARE Signaling Pathway to Alleviate Oxidative Stress

Premature ovarian insufficiency (POI) can result in lower fertility and shorten the female reproductive span. Bushen-Culuan Decoction (BCD) is a traditional Chinese medication utilized for treating POI for many years. We previously observed that BCD protects against further deterioration of the ovarian reserve of POI patients, however, the underlying mechanism has not been well studied. Our investigation seeks to evaluate the effect of BCD on POI induced by Tripterygium wilfordii polyglycosidium (TWP) and the likely mechanistic pathways, which we hypothesize may involve the Nrf2/ARE pathway. The body weights, estrous cycle, serum hormone levels, histological follicular analysis and quantification, levels of oxidative stress biomarkers in the ovarian tissue of POI mice models were evaluated. Western blotting and RT-PCR enabled quantification of the components of the Nrf2/ARE pathway. Our results showed that BCD restored hormonal profiles and estrous cycles of POI mice similar to those observed in healthy controls. BCD reduced the numbers of atretic follicles while increasing the number of primordial follicles. BCD facilitated lower 8-OHdG and MDA levels while increasing levels of key antioxidant enzymes including GSH-Px, CAT, and SOD. Furthermore, TWP increased Bach 1, Nrf2, and Keap 1 expressions at the translational level, while decreased that of HO-1. BCD treatment also promoted nuclear translocation rates of Bach 1 and Nrf2, suppressed Keap 1 protein expression, as well as raised HO-1 protein expression. Taken together, BCD likely augments ovarian reserve by activating the Nrf2/ARE signaling pathway, which stimulated higher levels of antioxidants and suppressed oxidative stress. BCD may be an important therapeutic compound in POI.

Avian eggshell coloration predicts shell-matrix protoporphyrin content

Avian eggshell pigmentation may provide information about a female's physiological condition, in particular her state of oxidative balance. Previously we found that female house wrens (Troglodytes aedon Vieillot, 1809) with lighter, less-maculated, and redder ground-colored shells were older and produced heavier offspring than females laying darker, browner eggs. The strong pro-oxidant protoporphyrin is responsible for this species' eggshell pigmentation, so differences in pigmentary coloration may be related to eggshell protoporphyrin content and reflect female oxidative balance and condition during egg-formation. Therefore, we tested the assumption that egg-surface coloration is related to the amount of protoporphyrin in the shell matrix. We analyzed digital photographs of eggs to determine maculation coverage as a measure of the overall ground coloration of the egg and its red-, green-, and blue-channel pixel values. Pigments were then extracted from these same eggs and analyzed using high-performance liquid chromatography. There was a strong, positive relationship between eggshell redness and protoporphyrin content of eggshells, but no relationship between percent maculation and protoporphyrin content. Thus, when older, larger females deposit more protoporphyrin in their eggshells, this may reflect a tolerance for high levels of circulating protoporphyrin or an effective mechanism for off-loading protoporphyrin into the eggshell matrix.

Reactive Oxygen Species in the Adverse Outcome Pathway Framework: Toward Creation of Harmonized Consensus Key Events

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are formed as a result of natural cellular processes, intracellular signaling, or as adverse responses associated with diseases or exposure to oxidizing chemical and non-chemical stressors. The action of ROS and RNS, collectively referred to as reactive oxygen and nitrogen species (RONS), has recently become highly relevant in a number of adverse outcome pathways (AOPs) that capture, organize, evaluate and portray causal relationships pertinent to adversity or disease progression. RONS can potentially act as a key event (KE) in the cascade of responses leading to an adverse outcome (AO) within such AOPs, but are also known to modulate responses of events along the AOP continuum without being an AOP event itself. A substantial discussion has therefore been undertaken in a series of workshops named "Mystery or ROS" to elucidate the role of RONS in disease and adverse effects associated with exposure to stressors such as nanoparticles, chemical, and ionizing and non-ionizing radiation. This review introduces the background for RONS production, reflects on the direct and indirect effects of RONS, addresses the diversity of terminology used in different fields of research, and provides guidance for developing a harmonized approach for defining a common event terminology within the AOP developer community.

Do low molecular weight antioxidants contribute to the Protection against oxidative damage? The interrelation between oxidative stress and low molecular weight antioxidants based on data from the MARK-AGE study

A redox steady state is important in maintaining vital cellular functions and is therefore homeostatically controlled by a number of antioxidative agents, the most important of which are enzymes. Oxidative Stress (OS) is associated with (or/and caused by) excessive production of damaging reactive oxygen and/or nitrogen species (ROS, RNS), which play a role in many pathologies. Because OS is a risk factor for many diseases, much effort (and money) is devoted to early diagnosis and treatment of OS. The desired benefit of the "identify (OS) and treat (by low molecular weight antioxidants, LMWA)" approach is to enable selective treatment of patients under OS. The present work aims at gaining understanding of the benefit of the antioxidants based on interrelationship between the concentration of different OS biomarkers and LMWA. Both the concentrations of a variety of biomarkers and of LMWA were previously determined and some analyses have been published by the MARK-AGE team. For the sake of simplicity, we assume that the concentration of an OS biomarker is a linear function of the concentration of a LMWA (if the association is due to causal relationship). A negative slope of this dependence (and sign of the correlation coefficient) can be intuitively expected for an antioxidant, a positive slope indicates that the LMWA is pro-oxidative, whereas extrapolation of the OS biomarker to [LMWA] = 0 is an approximation of the concentration of the OS biomarker in the absence of the LMWA. Using this strategy, we studied the effects of 12 LMWA (including tocopherols, carotenoids and ascorbic acid) on the OS status, as observed with 8 biomarkers of oxidative damage (including malondialdehyde, protein carbonyls, 3-nitrotyrosine). The results of this communication show that in a cross-sectional study the LMWA contribute little to the redox state and that different "antioxidants" are very different, so that single LMWA treatment of OS is not scientifically justified assuming our simple model. In view of the difficulty of quantitating the OS and the very different effects of various LMWA, the use of the "identify and treat" approach is questionable.

Biomarkers of Oxidative Stress and Antioxidant Defense

A number of reactive oxygen and nitrogen species are produced during normal metabolism in human body. These species can be both radical and non-radical and have varying degrees of reactivity. Although they have some important functions in the human body, such as contributing to signal transmission and the immune system, their presence must be balanced by the antioxidant defense system. The human body has an excellent intrinsic enzymatic antioxidant system in addition to different non-enzymatic antioxidants having small molecular masses. An extrinsic source of antioxidants are foodstuffs such as fruits, vegetables, herbs and spices, mostly rich in polyphenols. When the delicate biochemical balance between oxidants and antioxidants is disturbed in favor of oxidants, "oxidative stress" conditions emerge, under which reactive species can cause oxidative damage to biomacromolecules such as proteins, carbohydrates, lipids and DNA. This oxidative damage is often associated with cancer, aging, and neurodegenerative disorders. Because reactive species are extremely short-lived, it is almost impossible to measure their concentrations directly. Although there are certain methods such as ESR / EPR that serve this purpose, they have some disadvantages and are quite costly systems. Therefore, products generated from oxidative damage of proteins, lipids and DNA are often used to quantify the extent of oxidative damage rather than direct measurement of reactive species. These oxidative damage products are usually known as biomarkers. Determination of the concentrations of these biomarkers and changes in the concentration of protective antioxidants can provide useful information for avoiding certain diseases and keep healthy conditions.

Interplay between reactive oxygen and nitrogen species in living organisms

In living organisms most oxygen consumed is reduced to water via four-electron reduction. However, few percentages of oxygen are reduced by consecutive one electron mechanisms giving rise to superoxide anion radical, (O₂^•-), hydrogen peroxide (H₂O₂) and hydroxyl radical (HO^•) and their derivatives collectively called reactive oxygen species (ROS). Nitric oxide (^•NO) is produced at oxidation of arginine by nitric oxide synthase (NOS) or at reduction of nitrites by diverse reductases. Interaction of ^•NO with O₂^•- results in formation of peroxinitrite (ONOO^-), a powerful oxidant. Additionally, H₂O₂ can interact with ^•NO resulting in HO^• production. Nitric oxide and its derivatives are collectively called reactive nitrogen species (RNS) and together with ROS they form a group of so-called reactive oxygen/nitrogen species (RONS). Nonspecific effects of RONS are related to their interaction with various components of living organisms, whereas specific effects are based mainly on interaction with specific proteins containing [Fe-S]-clusters and thiol groups of cysteine residues. Most early ROS studies were mainly focused on their deleterious effects, whereas now more delicate mechanisms of their involvement in signaling and toxic processes are under inspection. Studies of RNS activities in biological systems started from their vasodilating effects which lead to discovery of activation of soluble guanylate cyclase. Interestingly, at low ROS and RNS concentrations signaling effects prevail, whereas at their high concentrations they affect biological systems inhibiting due to massive oxidation of cellular components.

The effects of cocoa flavanols on indices of muscle recovery and exercise performance: a narrative review

Exercise-induced muscle damage (EIMD) is associated with oxidative stress and inflammation, muscle soreness, and reductions in muscle function. Cocoa flavanols (CF) are (poly)phenols with antioxidant and anti-inflammatory effects and thus may attenuate symptoms of EIMD. The purpose of this narrative review was to collate and evaluate the current literature investigating the effect of CF supplementation on markers of exercise-induced oxidative stress and inflammation, as well as changes in muscle function, perceived soreness, and exercise performance. Acute and sub-chronic intake of CF reduces oxidative stress resulting from exercise. Evidence for the effect of CF on exercise-induced inflammation is lacking and the impact on muscle function, perceived soreness and exercise performance is inconsistent across studies. Supplementation of CF may reduce exercise-induced oxidative stress, with potential for delaying fatigue, but more evidence is required for any definitive conclusions on the impact of CF on markers of EIMD.

Oxidative Stress and Antioxidant Pathway in Allergic Rhinitis

Oxidative stress is the cause and consequence of redox metabolism in various physiological and pathological conditions. Understanding the molecular pathways underlying oxidative stress and the role of antioxidants could serve as the key to helping treat associated diseases. Allergic rhinitis is a condition that deteriorates the daily function and quality of life of afflicted individuals and is associated with a high socioeconomic burden and prevalence. Recent studies have focused on the role of oxidative stress and antioxidants in allergic rhinitis. This review discusses animal and clinical studies on oxidative markers and the potential therapeutic dietary antioxidants for allergic rhinitis.

In situ assessment of genetic and epigenetic alterations in frog Rana plancyi and Rana limnocharis inhabiting aquatic ecosystems associated with Pb/Zn/Cu mining

Exploration for metallic minerals leads to severe trace metal contamination, thus the ecological risk to aquatic organisms near mining regions has attracted widespread attention. In this study, two species of frog Rana plancyi and Rana limnocharis were collected as amphibian models to explore the genetic and epigenetic effects of trace metals in Dexing mining region. The results indicated that the surface water was heavily contaminated with trace metals and the two species of frog have high bioconcentration of trace metals in the liver. Trace metals disrupted the redox balance and increased reactive oxygen species levels. DNA strand breaks and increased 8-hydroxy-2'-deoxyguanosine levels were observed in the genomic DNA of frogs. Global DNA hypomethylation was found in the liver, which indicated adverse epigenetic effects on frogs. Overall, the study demonstrated that there was significant genotoxicity and epigenotoxicity of aquatic organisms living around the mining region. DNA damage and global DNA methylation are promising biomarkers for assessment of the ecological risk of trace metal pollution in aquatic amphibian frogs.

Redox-related biomarkers in human cardiovascular disease - classical footprints and beyond

Global epidemiological studies show that chronic non-communicable diseases such as atherosclerosis and metabolic disorders represent the leading cause of premature mortality and morbidity. Cardiovascular disease such as ischemic heart disease is a major contributor to the global burden of disease and the socioeconomic health costs. Clinical and epidemiological data show an association of typical oxidative stress markers such as lipid peroxidation products, 3-nitrotyrosine or oxidized DNA/RNA bases with all major cardiovascular diseases. This supports the concept that the formation of reactive oxygen and nitrogen species by various sources (NADPH oxidases, xanthine oxidase and mitochondrial respiratory chain) represents a hallmark of the leading cardiovascular comorbidities such as hyperlipidemia, hypertension and diabetes. These reactive oxygen and nitrogen species can lead to oxidative damage but also adverse redox signaling at the level of kinases, calcium handling, inflammation, epigenetic control, circadian clock and proteasomal system. The in vivo footprints of these adverse processes (redox biomarkers) are discussed in the present review with focus on their clinical relevance, whereas the details of their mechanisms of formation and technical aspects of their detection are only briefly mentioned. The major categories of redox biomarkers are summarized and explained on the basis of suitable examples. Also the potential prognostic value of redox biomarkers is critically discussed to understand what kind of information they can provide but also what they cannot achieve.

Correcting QUEST Magnetic Resonance Imaging-Sensitive Free Radical Production in the Outer Retina In Vivo Does Not Correct Reduced Visual Performance in 24-Month-Old C57BL/6J Mice

Purpose

To test the hypothesis that acutely correcting a sustained presence of outer retina free radicals measured in vivo in 24-month-old mice corrects their reduced visual performance.

Methods

Male C57BL/6J mice two and 24 months old were noninvasively evaluated for unremitted production of paramagnetic free radicals based on whether 1/T1 in retinal laminae are reduced after acute antioxidant administration (QUEnch-assiSTed [QUEST] magnetic resonance imaging [MRI]). Superoxide production was measured in freshly excised retina (lucigenin assay). Combining acute antioxidant administration with optical coherence tomography (i.e., QUEST OCT) tested for excessive free radical–induced shrinkage of the subretinal space volume. Combining antioxidant administration with optokinetic tracking tested for a contribution of uncontrolled free radical production to cone-based visual performance declines.

Results

At two months, antioxidants had no effect on 1/T1 in vivo in any retinal layer. At 24 months, antioxidants reduced 1/T1 only in superior outer retina. No age-related change in retinal superoxide production was measured ex vivo, suggesting that free radical species other than superoxide contributed to the positive QUEST MRI signal at 24 months. Also, subretinal space volume did not show evidence for age-related shrinkage and was unresponsive to antioxidants. Finally, visual performance declined with age and was not restored by antioxidants that were effective per QUEST MRI.

Conclusions

An ongoing uncontrolled production of outer retina free radicals as measured in vivo in 24 mo C57BL/6J mice appears to be insufficient to explain reductions in visual performance.

Linking biomarkers of oxidative stress and disease with flavonoid consumption: From experimental models to humans

Identification of the links among flavonoid consumption, mitigation of oxidative stress and improvement of disease in humans has significantly advanced in the last decades. This review used (−)-epicatechin (EC) as an example of dietary flavonoids, and inflammation, endothelial dysfunction/hypertension and insulin resistance/diabetes as paradigms of human disease. In these pathologies, oxidative stress is part of their development and/or their perpetuation. Evidence from both, rodent studies and characterization of mechanisms in cell cultures are encouraging and mostly support indirect antioxidant actions of EC and EC metabolites in endothelial dysfunction and insulin resistance. Human studies also show beneficial effects of EC on these pathologies based on biomarkers of disease. However, there is limited available information on oxidative stress biomarkers and flavonoid consumption to allow establishing conclusive associations. The evolving discovery of metabolites that could serve as reliable markers of intake of specific flavonoids constitutes a powerful tool to link flavonoid consumption to disease and prevention of oxidative stress in human populations.

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Flavonoid’s metabolism and concentration determine their antioxidant mechanisms.

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Except for the GI tract, flavonoids are relevant indirect antioxidants in organs and tissues.

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Flavonoid's health effects are not always linked to biomarkers of oxidative stress.

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(‒)-Epicatechin mitigates the redox deregulation involved in hypertension/T2D pathogenesis.

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More human studies will strength links among flavonoids, oxidative stress, and disease.

Biological effects, including oxidative stress and genotoxic damage, of polystyrene nanoparticles in different human hematopoietic cell lines

In recent years the terms "micro-/nanoplastics" (MNPLs) have caught special attention due to the increasing levels by which humans are exposed. Among MNPLs, polystyrene nanoparticles (PSNPs) are one of the most represented MNPLs in the environment. These tiny particles may enter into the human body, translocate through human barriers, interacting with blood and lymphatic immune cells, and reaching secondary organs. By using three different human leukocytic cell lines: Raji-B (B-lymphocytes), TK6 (lymphoblasts) and THP-1 (monocytes), we pursued to determine the effects of these PSNPs on the immune cell population. With this aim, the three cell lines were exposed to spherical PSNPs of about 50 nm of diameter and cytotoxicity, cellular uptake, reactive oxygen species (ROS) production, and genotoxicity were assessed at different time-points. Results show differences in all the measured endpoints, among the selected cell lines. Thus, whilst the monocytic THP-1 cells showed the highest particle internalization, no adverse effects were observed in such cells. On the other side, although Raji-B and TK6 showed lesser PSNPs uptake, mild toxicity, ROS production and genotoxicity were detected. These results highlight the importance of the cell line selection when the biological effects of PSNPs are evaluated.

Oxidative Stress: Concept and Some Practical Aspects

Oxidative stress is defined as “an imbalance between oxidants and antioxidants in favor of the oxidants, leading to a disruption of redox signaling and control and/or molecular damage”. This Commentary presents basic features of this global concept which has attracted interest in biology and medicine. The term “antioxidants” in cellular defense against oxidants predominantly includes antioxidant enzymes with their substrates and coenzymes. Exogenous low-molecular-mass compounds also have a role, but this is more limited. Multiple biomarkers of damage due to oxidative stress have been identified for different molecular classes (protein, lipid, carbohydrate, and DNA), and the current state of practical aspects in health and disease is delineated.

Targeting Oxidative Stress for Disease Prevention and Therapy: Where Do We Stand, and Where Do We Go from Here

Oxidative stress (OxS) is one of the main processes related to aging and a common denominator of many different chronic/degenerative diseases (e.g., cardiovascular and neurodegenerative conditions and cancer). Thus, its potential modulation by supplementation/pharmacological therapy caused a lot of interest. However, these expectations have been mitigated by the obtainment of controversial results (beneficial, null, or adverse effects) following antioxidant interventions. Here, we discuss the current understanding of OxS assessment in health and disease, challenges and the potential of its evaluation in clinical practice, and available and future development for supplementation and pharmacologic strategies targeting OxS.