Circadian rhythmicity of whole-blood glutathione in healthy subjects

Methodological confounds of measuring urinary oxidative stress in wild animals

Biomarkers of oxidative stress (OS) are useful in addressing a wide range of research questions, but thus far, they have had limited application to wild mammal populations due to a reliance on blood or tissue sampling. A shift toward non-invasive measurement of OS would allow field ecologists and conservationists to apply this method more readily. However, the impact of methodological confounds on urinary OS measurement under field conditions has never been explicitly investigated. We combined a cross-sectional analysis with a field experiment to assess the impact of four potential methodological confounds on OS measurements: (1) time of sampling, (2) environmental contamination from foliage; (3) delay between sample collection and flash-freezing in liquid nitrogen; and (4) sample storage of up to 15 months below -80°C. We measured DNA oxidative damage (8-hydroxy-2'-deoxyguanosine, 8-OHdG), lipid peroxidation (malondialdehyde, MDA), total antioxidant capacity (TAC), and uric acid (UA) in 167 urine samples collected from wild Zanzibar red colobus (Piliocolobus kirkii). We found that MDA was higher in samples collected in the morning than in the afternoon but there were no diurnal patterns in any of the other markers. Contamination of samples from foliage and length of time frozen at -80°C for up to 15 months did not affect OS marker concentrations. Freezing delay did not affect OS levels cross-sectionally, but OS values from individual samples showed only moderate-to-good consistency and substantial rank-order reversals when exposed to different freezing delays. We recommend that diurnal patterns of OS markers and the impact of storage time before and after freezing on OS marker concentrations be considered when designing sampling protocols. However, given the high stability we observed for four OS markers subject to a variety of putative methodological confounds, we suggest that urinary OS markers provide a valuable addition to the toolkit of field ecologists and conservationists within reasonable methodological constraints.

Variations in Oxidative Stress Levels in 3 Days Follow-up in Ultramarathon Mountain Race Athletes

Spanidis, Y, Stagos, D, Orfanou, M, Goutzourelas, N, Bar-or, D, Spandidos, D, and Kouretas, D. Variations in oxidative stress levels in 3 days follow-up in ultramarathon mountain race athletes. J Strength Cond Res 31(3): 582-594, 2017-The aim of the present study was the monitoring of the redox status of runners participating in a mountain ultramarathon race of 103 km. Blood samples from 12 runners were collected prerace and 24, 48, and 72 hours postrace. The samples were analyzed by using conventional oxidative stress markers, such as protein carbonyls (CARB), thiobarbituric acid reactive substances (TBARS), total antioxidant capacity (TAC) in plasma, as well as glutathione (GSH) levels and catalase (CAT) activity in erythrocytes. In addition, 2 novel markers, the static oxidation-reduction potential marker (sORP) and the capacity oxidation-reduction potential (cORP), were measured in plasma. The results showed significant increase in sORP levels and significant decrease in cORP and GSH levels postrace compared with prerace. The other markers did not exhibit significant changes postrace compared with prerace. Furthermore, an interindividual analysis showed that in all athletes but one sORP was increased, whereas cORP was decreased. Moreover, GSH levels were decreased in all athletes at least at 2 time points postrace compared with prerace. The other markers exhibited great variations between different athletes. In conclusion, ORP and GSH markers suggested that oxidative stress has existed even 3 days post ultramarathon race. The practical applications from these results would be that the most effective markers for short-term monitoring of ultramarathon mountain race-induced oxidative stress were sORP, cORP, and GSH. Also, administration of supplements enhancing especially GSH is recommended during ultramarathon mountain races to prevent manifestation of pathological conditions.

Going retro: Oxidative stress biomarkers in modern redox biology

The field of redox biology is inherently intertwined with oxidative stress biomarkers. Oxidative stress biomarkers have been utilized for many different objectives. Our analysis indicates that oxidative stress biomarkers have several salient applications: (1) diagnosing oxidative stress, (2) pinpointing likely redox components in a physiological or pathological process and (3) estimating the severity, progression and/or regression of a disease. On the contrary, oxidative stress biomarkers do not report on redox signaling. Alternative approaches to gain more mechanistic insights are: (1) measuring molecules that are integrated in pathways linking redox biochemistry with physiology, (2) using the exomarker approach and (3) exploiting -omics techniques. More sophisticated approaches and large trials are needed to establish oxidative stress biomarkers in the clinical setting.

Redox regulation and pro-oxidant reactions in the physiology of circadian systems

Rhythms of approximately 24 h are pervasive in most organisms and are known as circadian. There is a molecular circadian clock in each cell sustained by a feedback system of interconnected "clock" genes and transcription factors. In mammals, the timing system is formed by a central pacemaker, the suprachiasmatic nucleus, in coordination with a collection of peripheral oscillators. Recently, an extensive interconnection has been recognized between the molecular circadian clock and the set of biochemical pathways that underlie the bioenergetics of the cell. A principle regulator of metabolic networks is the flow of electrons between electron donors and acceptors. The concomitant reduction and oxidation (redox) reactions directly influence the balance between anabolic and catabolic processes. This review summarizes and discusses recent findings concerning the mutual and dynamic interactions between the molecular circadian clock, redox reactions, and redox signaling. The scope includes the regulatory role played by redox coenzymes (NAD(P)+/NAD(P)H, GSH/GSSG), reactive oxygen species (superoxide anion, hydrogen peroxide), antioxidants (melatonin), and physiological events that modulate the redox state (feeding condition, circadian rhythms) in determining the timing capacity of the molecular circadian clock. In addition, we discuss a purely metabolic circadian clock, which is based on the redox enzymes known as peroxiredoxins and is present in mammalian red blood cells and in other biological systems. Both the timing system and the metabolic network are key to a better understanding of widespread pathological conditions such as the metabolic syndrome, obesity, and diabetes.

Circadian (about 24-hour) variation in malondialdehyde content and catalase activity of mouse erythrocytes

Lipid peroxidation is a part of normal metabolism that may cause biological molecule damage leading to the formation of several specific metabolites that include aldehydes of variable chains, such as malondialdehyde (MDA). These biological effects are controlled in vivo by a wide spectrum of enzymatic and non-enzymatic defense mechanisms among which catalase (CAT) is considered as an important regulator of oxidative stress. The present study aimed to investigate the possible relationship between the temporal patterns of the formation of MDA and the activity of CAT in the erythrocytes of mice. Twenty-four-hour studies were performed on male Swiss albino mice, 12 weeks old, synchronized to a 12:12 light: dark cycle for 3 weeks. Different and comparable groups of animals (n = 10) were sacrificed at an interval of 4 hours (1, 5, 9, 13, 17, and 21 hours after light onset (HALO)). The levels of erythrocyte MDA concentration and CAT activity both significantly (analysis of variance: F = 6.4, P < 0.002) varied according to the time of sampling under non-stressed conditions. The characteristics of the waveform describing the temporal patterns differed between the two studied variables, e.g. MDA content showing one peak (≅21 HALO) and CAT activity showing three peaks (≅9, 17, and 21 HALO). Cosinor analysis revealed a significant (adjusted Cosinor: P ≤ 0.018) circadian (τ ≅ 24 hours) rhythm in MDA level and no statistically significant rhythmicity in CAT activity. The differences and the absence of correlation between the curve patterns of erythrocyte MDA content and CAT activity under physiological conditions are hypothesized to explain that variation in lipid peroxidation may depend on several factors. Moreover, the identification of peak/trough levels of MDA accumulation in erythrocytes may reflect the degree of oxidative stress in these blood cells. In addition, the observed significant time-of-day effect suggests that, in both clinical and scientific settings, appropriate comparison of MDA production and CAT activity levels can only be achieved on data obtained at the same time of day.

Reductive stress after exercise: The issue of redox individuality

Exercise has been consistently used as an oxidant stimulus in redox biology studies. However, previous studies have focused on group differences and did not examine individual differences. As a result, it remains untested whether all individuals experience oxidative stress after acute exercise. Therefore, the main aim of the present study was to investigate whether some individuals exhibit unexpected responses after an acute eccentric (i.e., muscle-damaging) exercise session. Ninety eight (N = 98) young men performed an isokinetic eccentric exercise bout with the knee extensors. Plasma, erythrocytes and urine samples were collected immediately before and 2 days post-exercise. Three commonly used redox biomarkers (F₂-isoprostanes, protein carbonyls and glutathione) were assayed. As expected, the two oxidant biomarkers (F₂-isoprostanes and protein carbonyls) significantly increased 2 days after exercise (46% and 61%, respectively); whereas a significant decrease in glutathione levels (by −21%) was observed after exercise. A considerable number of the participants exhibited changes in the levels of biomarkers in the opposite, unexpected direction than the group average. More specifically, 13% of the participants exhibited a decrease in F₂-isoprostanes and protein carbonyls and 10% of the participants exhibited an increase in glutathione levels. Furthermore, more than 1 out of 3 individuals exhibited either unexpected or negligible (from 0% to ± 5%) responses to exercise in at least one redox biomarker. It was also observed that the initial values of redox biomarkers are important predictors of the responses to exercise. In conclusion, although exercise induces oxidative stress in the majority of individuals, it can induce reductive stress or negligible stress in a considerable number of people. The data presented herein emphasize that the mean response to a redox stimulus can be very misleading. We believe that the wide variability (including the cases of reductive stress) described is not limited to the oxidant stimulus used and the biomarkers selected.

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Exercise may induce reductive stress instead of the expected oxidative stress.

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The initial values of biomarkers are major predictors of the responses to exercise.

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The mean response of a group to a redox stimulus can be misleading.

Day to Day Variability and Reliability of Blood Oxidative Stress Markers within a Four-Week Period in Healthy Young Men

The present study aimed to determine the day to day variability and reliability of several blood oxidative stress markers at rest in a healthy young cohort over a four-week period. Twelve apparently healthy resistance trained males (24.6 ± 3.0 yrs) were tested over 7 visits within 4 weeks with at least 72 hrs between visits at the same time of day. Subjects rested 30 minutes prior to blood being obtained by vacutainer. Results. The highest IntraClass correlations (ICC's) were obtained for protein carbonyls (PC) and oxygen radical absorbance capacity (ORAC) (PC = 0.785 and ORAC = 0.780). Cronbach's α reliability score for PC was 0.967 and for ORAC was 0.961. The ICC's for GSH, GSSG, and the GSSG/TGH ratio ICC were 0.600, 0.573, and 0.570, respectively, with Cronbach's α being 0.913, 0.904, and 0.903, respectively. Xanthine oxidase ICC was 0.163 and Cronbach's α was 0.538. Conclusions. PC and ORAC demonstrated good to excellent reliability while glutathione factors had poor to excellent reliability. Xanthine oxidase showed poor reliability and high variability. These results suggest that the PC and ORAC markers were the most stable and reliable oxidative stress markers in blood and that daily changes across visits should be considered when interpreting resting blood oxidative stress markers.

Evaluation of the antioxidant properties of N-acetylcysteine in human platelets: prerequisite for bioconversion to glutathione for antioxidant and antiplatelet activity

N-Acetylcysteine (NAC) is a frequently used "antioxidant" in vitro, but the concentrations applied rarely correlate with those encountered with oral dosing in vivo. Here, we investigated the in vitro antioxidant and antiplatelet properties of NAC at concentrations (10-100 microM) that are achievable in plasma with tolerable oral dosing. The impact of NAC pretreatment (2 hours) on aggregation of platelets from healthy volunteers in response to thrombin and adenosine diphosphate and on platelet-derived nitric oxide (NO) was examined. NAC was found to be a weak reducing agent and a poor antioxidant compared with glutathione (reduced form) (GSH). However, platelets treated with NAC showed enhanced antioxidant activity and depression of reactive oxygen species generation associated with increases in intraplatelet GSH levels. An approximately 2-fold increase in NO synthase-derived nitrite was observed with 10 microM NAC treatment, but the effect was not concentration dependent. Finally, NAC significantly reduced both thrombin-induced and adenosine diphosphate-induced platelet aggregation. NAC should be considered a weak antioxidant that requires prior conversion to GSH to convey antioxidant and antithrombotic benefit at therapeutically relevant concentrations. Our results suggest that NAC might be an effective antiplatelet agent in conditions where increased oxidative stress contributes to heightened risk of thrombosis but only if the intraplatelet machinery to convert it to GSH is functional.

Glutathione and Glutathione Peroxidase Activities in Blood of Patients in Early Stages Following Kidney Transplantation

This study focuses on glutathione (GSH) level in red blood cells, as well as on glutathione peroxidases (GSH-Px) activities in red blood cells and in plasma of chronic renal failure (CRF) patients following renal transplantation. We want to focus our main attention on plasma GSH-Px, the selenoenzyme that is synthesized primarily in the kidney. In CRF patients, activity of this enzyme is significantly reduced, and the reduction decreases with the progress of the disease, reaching in the end-stage 20% to 30% of the activity of healthy patients. We have shown that following renal transplantation the activity of plasma GSH-Px is restored very rapidly, and 2 weeks after surgery it reached the value of the control group. Red blood cell GSH level is significantly higher in CRF patients, and following transplantation, no significant changes were observed. Red blood cell GSH-Px activity before transplantation was the same as in healthy patients and did not change significantly after surgery.

Diurnal variations in salivary protein carbonyl levels in normal and cognitively impaired human subjects

Oxidative stress has been documented in tissues and biofluids of subjects with sporadic Alzheimer disease (AD) and mild cognitive impairment (MCI). The aim of this study was to determine whether (a) salivary protein carbonyls are elevated in AD and MCI subjects, (b) salivary protein carbonyl contents in these groups exhibit diurnal variation, and (c) apolipoprotein E epsilon 4 (apoE epsilon 4) carrier status impacts salivary carbonyl concentrations or rhythmicity in the AD and MCI cohorts. Unstimulated saliva was collected at fixed intervals between 8 AM: and 10 PM: from 15 AD subject , 21 MCI subjects, and 30 cognitively-intact controls. Salivary protein carbonyl concentrations were measured by ELISA. ApoE genotyping was performed on the AD and MCI individuals. For all groups, mean protein carbonyl contents were significantly elevated at 2 PM: relative to other time points surveyed. Mean salivary protein carbonyl concentrations did not differ among the diagnostic groups. ApoE epsilon 4 carriers exhibited less temporal variation in salivary protein carbonyls relative to noncarriers. Thus, protein carbonyl content exhibits diurnal variation in adult human saliva. ApoE epsilon 4 carrier status may impact oropharyngeal disease expression by attenuating the inherent diurnal variability in salivary redox homeostasis. Salivary protein carbonyls do not differentiate AD and MCI from normal individuals. In conclusion, oxidative stress has been documented in tissues and biofluids of subjects with sporadic AD and MCI. This article demonstrates that levels of protein carbonyls, a marker of oxidative stress, exhibit robust diurnal variation in the saliva of normal elderly, MCI, and AD subjects. Apolipoprotein E epsilon 4 allele carrier status may attenuate this temporal variability in salivary redox homeostasis and thereby impact the natural history of oropharyngeal diseases.

Circadian rhythms, oxidative stress, and antioxidative defense mechanisms

Endogenous circadian and exogenously driven daily rhythms of antioxidative enzyme activities and of low molecular weight antioxidants (LMWAs) are described in various phylogenetically distant organisms. Substantial amplitudes are detected in several cases, suggesting the significance of rhythmicity in avoiding excessive oxidative stress. Mammalian and/or avian glutathione peroxidase and, as a consequence, glutathione reductase activities follow the rhythm of melatonin. Another hint for an involvement of melatonin in the control of redox processes is seen in its high-affinity binding to cytosolic quinone reductase 2, previously believed to be a melatonin receptor. Although antioxidative protection by pharmacological doses of melatonin is repeatedly reported, explanations of these findings are still insufficient and their physiological and chronobiological relevance is not yet settled. Recent data indicate a role of melatonin in the avoidance of mitochondrial radical formation, a function which may prevail over direct scavenging. Rhythmic changes in oxidative damage of protein and lipid molecules are also reported. Enhanced oxidative protein modification accompanied by a marked increase in the circadian amplitude of this parameter is detected in the Drosophila mutant rosy, which is deficient in the LMWA urate. Preliminary evidence for the significance of circadian rhythmicity in diminishing oxidative stress comes from clock mutants. In Drosophila, moderately enhanced protein damage is described for the arrhythmic and melatonin null mutant per0, but even more elevated, periodic damage is found in the short-period mutant per(s), synchronized to LD 12:12. Remarkably large increases in oxidative protein damage, along with impairment of tissue integrity and--obviously insufficient--compensatory elevations in protective enzymes are observed in a particularly vulnerable organ, the Harderian gland, of another short-period mutant tau, in the Syrian hamster. Mice deficient in the per2 gene homolog are reported to be cancer-prone, a finding which might also relate to oxidative stress. In the dinoflagellate Lingulodinium polyedrum [Gonyaulax polyedra], various treatments that cause oxidative stress result in strong suppressions of melatonin and its metabolite 5-methoxytryptamine (5-MT) and to secondary effects on overt rhythmicity. The glow maximum, depending on the presence of elevated 5-MT at the end of subjective night, decreases in a dose-dependent manner already under moderate, non-lethal oxidative stress, but is restored by replenishing melatonin. Therefore, a general effect of oxidative stress may consist in declines of easily oxidizable signaling molecules such as melatonin, and this can have consequences on the circadian intraorganismal organization and expression of overt rhythms. Recent findings on a redox-sensitive input into the core oscillator via modulation of NPAS2/BMAL1 or CLK/BMAL1 heterodimer binding to DNA indicate a direct influence of cellular redox balance, including oxidative stress, on the circadian clock.