Methods to assess free radicals and oxidative stress in biological systems

The effect of ingestion of red dragon fruit extract on levels of malondialdehyde and superoxide dismutase after strenuous exercise in rats (Rattus norvegicus)

Background: Prolonged activation of skeletal muscles causes a decrease in the production of fatigue. Exercise with strenuous intensity causes an increase in Reactive Oxygen Species (ROS). An increase in free radicals causes oxidative stress resulting in damage to cell function to mitochondrial dysfunction, and fatigue. This study aimed to determine the antioxidant potential of red dragon fruit (RDF) to delay fatigue due to oxidative stress, which improves cell function in mitochondria.

Methods: 25 male rats (Rattus norvegicus) aged three months were divided into five groups: Group K1 was N.A. (No Activity) but drinking and eating; Group K2 performed strenuous exercise without RDF treatment; Groups 3, 4, and 5 (P1, P2 and P3, respectively) performed strenuous exercise and were treated with 75 mg kg ^-1.bw, 150 mg kg ^-1.bw, and 300 mg kg ^-1.bw of RDF extract, respectively. The exercise for the rats involved intense swimming for 20 minutes  a day three time a week for fouweeks.  Malondialdehyde (MDA) dan SOD was measured with the ELISA and histopathology for muscle soleus and lung tissue.

Results: Strenuous exercise followed by RDF extract ingestion was compared for fatigue in terms of duration and time; before (24.55±1.38 minute) and after (95.31±7.82 minute) and led to a significant difference of 39% (p<0.01). The study also compared MDA before and after RDF extract ingestion in the K2 vs. the P1 group (p<0.05). At the same time, P2 differed more significantly (p<0.01). This indicated a spread of free radicals and featured histopathological damage of muscle cells. However, ingestion of RDF extract leads to improvement of soleus muscle cells; thus, repairs cell function, delaying fatigue.

Conclusion: This study confirmed that strenuous exercise, which causes an increase in ROS, intensifies free radicals with RDF extract ingestion and declines oxidative stress, repairing cell function and delaying fatigue.

Effects of Red-Fleshed Pitaya (Selenicereus polyrhizus) Ingestion after Strenuous Exercise on Creatine Kinase and Mitochondrial Function in Rat Muscle Cells

BACKGROUND: Free radicals formed during strenuous exercise through an increase in reactive oxygen species induce damage to tissues (e.g., muscle and liver) and cause oxidative damage to cells, resulting in mitochondrial dysfunction. AIM: As an effective method to repair mitochondrial muscle cell function, this study investigated the effects of red-fleshed pitaya (RFP) ingestion on creatine kinase (CK), which is a biomarker for muscle tissue damage, and malondialdehyde (MDA) levels during strenuous exercise. METHODS: This study involved 25 3-month-old male rats with an average weight of 200 g. The RFP extract was obtained through ethanol extraction and concentrated using an air-drying method. Rats were randomly allocated into five groups as follows: Two control groups (K1 [no-exercise, no RFP] and K2 [exercise, no RFP]) and three test groups (P1, P2, and P3; subjected to exercise and treated with 75, 150, and 300 mg kg−1 body weight of RFP, respectively). The exercise was in the form of swimming for 20 min 3 times/week for 31 days. CK and MDA were measured through an enzyme-linked immunosorbent assay, and histopathological examinations were performed through hematoxylin and eosin staining of rat muscles. RESULTS: The MDA levels after the ingestion of RFP extracts were compared between the K2 group and the P1, P2, and P3 groups. The results showed significant differences (p < 0.05 for P1 and P2, and p < 0.01 for P3), indicating the production of free radicals and CK, with features of damaged muscle cells based on histopathology. Ingestion of the RFP extract led to improvements in soleus muscle cells, resulting in cell function repair. CONCLUSION: Levels of MDA and CK increased during exercise, which caused significant muscle damage. However, after treatment with the RFP extract, the levels of both markers decreased. Thus, strenuous exercise causes an increase in reactive oxygen species, resulting in increased free radical levels. RFP ingestion decreased oxidative stress levels, thus repairing mitochondrial cell function.

Methods to evaluate the scavenging activity of antioxidants toward reactive oxygen and nitrogen species (IUPAC Technical Report)

This project was aimed to identify the quenching chemistry of biologically important reactive oxygen and nitrogen species (ROS/RNS, including radicals), to show antioxidant action against reactive species through H‐atom and electron transfer reactions, and to evaluate the ROS/RNS scavenging activity of antioxidants with existing analytical methods while emphasizing the underlying chemical principles and advantages/disadvantages of these methods. In this report, we focused on the applications and impact of existing assays on potentiating future research and innovations to evolve better methods enabling a more comprehensive study of different aspects of antioxidants and to provide a vocabulary of terms related to antioxidants and scavengers for ROS/RNS. The main methods comprise the scavenging activity measurement of the hydroxyl radical (•OH), dioxide(•1–) (O2 •–: commonly known as the superoxide radical), dihydrogen dioxide (H2O2: commonly known as hydrogen peroxide), hydroxidochlorine (HOCl: commonly known as hypochlorous acid), dioxidooxidonitrate(1–) (ONOO−: commonly known as the peroxynitrite anion), and the peroxyl radical (ROO•). In spite of the diversity of methods, there is currently a great need to evaluate the scavenging activity of antioxidant compounds in vivo and in vitro. In addition, there are unsatisfactory methods frequently used, such as non-selective UV measurement of H2O2 scavenging, producing negative errors due to incomplete reaction of peroxide with flavonoids in the absence of transition metal ion catalysts. We also discussed the basic mechanisms of spectroscopic and electrochemical nanosensors for measuring ROS/RNS scavenging activity of antioxidants, together with leading trends and challenges and a wide range of applications. This project aids in the identification of reactive species and quantification of scavenging extents of antioxidants through various assays, makes the results comparable and more understandable, and brings a more rational basis to the evaluation of these assays and provides a critical evaluation of existing ROS/RNS scavenging assays to analytical, food chemical, and biomedical/clinical communities by emphasizing the need for developing more refined, rapid, simple, and low‐cost assays and thus opening the market for a wide range of analytical instruments, including reagent kits and sensors.

The effect of ingestion of red dragon fruit extract on levels of malondialdehyde and superoxide dismutase after strenuous exercise in rats ( Rattus norvegicus)

Background: Prolonged activation of skeletal muscles causes a decrease in the production of fatigue. Exercise with strenuous intensity causes an increase in Reactive Oxygen Species (ROS). An increase in free radicals causes oxidative stress resulting in damage to cell function to mitochondrial dysfunction, and fatigue. This study aimed to determine the antioxidant potential of red dragon fruit (RDF) to delay fatigue due to oxidative stress, which improves cell function in mitochondria. Methods: 25 male rats (Rattus norvegicus) aged three months were divided into five groups: Group K1 was N.A. (No Activity) but drinking and eating; Group K2 performed strenuous exercise without RDF treatment; Groups 3, 4, and 5 (P1, P2 and P3, respectively) performed strenuous exercise and were treated with 75 mg kg -1.bw, 150 mg kg -1.bw, and 300 mg kg -1.bw of RDF extract, respectively. The exercise for the rats involved intense swimming for 20 minutes  a day three time a week for fouweeks.  Malondialdehyde (MDA) dan SOD was measured with the ELISA and histopathology for muscle soleus and lung tissue. Results: Strenuous exercise followed by RDF extract ingestion was compared for fatigue in terms of duration and time; before (24.55±1.38 minute) and after (95.31±7.82 minute) and led to a significant difference of 39% (p<0.01). The study also compared MDA before and after RDF extract ingestion in the K2 vs. the P1 group (p<0.05). At the same time, P2 differed more significantly (p<0.01). This indicated a spread of free radicals and featured histopathological damage of muscle cells. However, ingestion of RDF extract leads to improvement of soleus muscle cells; thus, repairs cell function, delaying fatigue. Conclusion: This study confirmed that strenuous exercise, which causes an increase in ROS, intensifies free radicals with RDF extract ingestion and declines oxidative stress, repairing cell function and delaying fatigue.

Reactive oxygen species in exercise and insulin resistance: Working towards personalized antioxidant treatment

Reactive oxygen species (ROS) are well known for their role in insulin resistance and the development of cardiometabolic disease including type 2 diabetes mellitus (T2D). Conversely, evidence supports the notion that ROS are a necessary component for glucose cell transport and adaptation to physiological stress including exercise and muscle contraction. Although genetic rodent models and cell culture studies indicate antioxidant treatment to be an effective strategy for targeting ROS to promote health, human findings are largely inconsistent. In this review we discuss human research that has investigated antioxidant treatment and glycemic control in the context of health (healthy individuals and during exercise) and disease (insulin resistance and T2D). We have identified key factors that are likely to influence the effectiveness of antioxidant treatment: 1) the context of treatment including whether oxidative distress or eustress is present (e.g., hyperglycemia/lipidaemia or during exercise and muscle contraction); 2) whether specific endogenous antioxidant deficiencies are identified (redox screening); 3) whether antioxidant treatment is specifically designed to target and restore identified deficiencies (antioxidant specificity); 4) and the bioavailability and bioactivity of the antioxidant which are influenced by treatment dose, duration, and method of administration. The majority of human research has failed to account for these factors, limiting their ability to robustly test the effectiveness of antioxidants for health promotion and disease prevention. We propose that a modern "redox screening" and "personalized antioxidant treatment" approach is required to robustly explore redox regulation of human physiology and to elicit more effective antioxidant treatment in humans.

Induction of DNA damage as a consequence of occupational exposure to crystalline silica: A review and meta-analysis

About 40 million workers are occupationally exposed to crystalline silica (CS) which was classified as a human carcinogen by the IARC. It is assumed that damage of the genetic material via inflammation and reactive oxygen species by CS lead to formation of malignant cells. We conducted a systematic literature search to find out if inhalation of CS containing dusts at workplaces causes damage of the genetic material. Thirteen studies were found eligible for this review, in most of them (n = 9) micronuclei (MN) which reflect structural/numerical chromosomal aberrations were monitored in lymphocytes and/or in exfoliated buccal cells. In 5 investigations DNA damage was measured in blood cells in single cell gel electrophoresis (comet) experiments. Frequently studied groups were potters, stone cutters, miners and construction workers. Results of meta-analyses show that exposure to CS causes formation of MN and DNA breaks, the overall ratio values were in exposed workers 2.06- and 1.96-fold higher than in controls, respectively. Two studies reported increased levels of oxidized guanine, and higher levels of DNA adducts with malondialdehyde indicating that exposure to CS leads to oxidative damage. The exposure of the workers to CS was quantified only in two studies, information concerning the size and chemical structures of the particles is lacking in most investigations. Therefore, it is not possible to use the results to derive occupational exposure limits of workers to CS which vary strongly in different countries. Nevertheless, the evaluation of the current state of knowledge shows that biomonitoring studies in which damage of the genetic material is measured in CS exposed workers can contribute to assess adverse health effects as consequence of DNA instability in specific occupations.

Exercise and Glycemic Control: Focus on Redox Homeostasis and Redox-Sensitive Protein Signaling

Physical inactivity, excess energy consumption, and obesity are associated with elevated systemic oxidative stress and the sustained activation of redox-sensitive stress-activated protein kinase (SAPK) and mitogen-activated protein kinase signaling pathways. Sustained SAPK activation leads to aberrant insulin signaling, impaired glycemic control, and the development and progression of cardiometabolic disease. Paradoxically, acute exercise transiently increases oxidative stress and SAPK signaling, yet postexercise glycemic control and skeletal muscle function are enhanced. Furthermore, regular exercise leads to the upregulation of antioxidant defense, which likely assists in the mitigation of chronic oxidative stress-associated disease. In this review, we explore the complex spatiotemporal interplay between exercise, oxidative stress, and glycemic control, and highlight exercise-induced reactive oxygen species and redox-sensitive protein signaling as important regulators of glucose homeostasis.

Reserpine Inhibit the JB6 P+ Cell Transformation Through Epigenetic Reactivation of Nrf2-Mediated Anti-oxidative Stress Pathway

Nuclear factor erythroid-2 related factor 2 (Nrf2) is a crucial transcription factor that regulates the expression of defensive antioxidants and detoxification enzymes in cells. In a previous study, we showed that expression of the Nrf2 gene is regulated by an epigenetic modification. Rauvolfia verticillata, a traditional Chinese herbal medicine widely used in China, possesses anticancer and antioxidant effects. In this study, we investigated how Nrf2 is epigenetically regulated by reserpine, the main active component in R. verticillata, in mouse skin epidermal JB6 P+ cells. Reserpine induced ARE (antioxidant response element)-luciferase activity in HepG2-C8 cells. Accordingly, in JB6 P+ cells, it upregulated the mRNA and protein levels of Nrf2 and its downstream target genes heme oxygenase-1 (HO-1) and

NAD(P)H

quinone oxidoreductase 1 (NQO1), while it only increased the protein level of UDP-glucuronosyltransferase 1A1 (UGT1A1). Furthermore, reserpine decreased the TPA (12-O-tetradecanoylphorbol-13-acetate)-induced colony formation of JB6 cells in a dose-dependent manner. DNA sequencing and methylated DNA immunoprecipitation further demonstrated the demethylation effect of reserpine on the first 15 CpGs of the Nrf2 promoter in JB6 P+ cells. Reserpine also reduced the mRNA and protein expression of DNMT1 (DNA methyltransferase 1), DNMT3a (DNA methyltransferases 3a), and DNMT3b (DNA methyltransferases 3b). Moreover, reserpine induced Nrf2 expression via an epigenetic pathway in skin epidermal JB6 P+ cells, enhancing the protective antioxidant activity and decreasing TPA-induced cell transformation. These results suggest that reserpine exhibits a cancer preventive effect by reactivating Nrf2 and inducing the expression of target genes involved in cellular protection, potentially providing new insight into the chemoprevention of skin cancer using reserpine.

Free Radical Scavenging and Cellular Antioxidant Properties of Astaxanthin

Astaxanthin is a coloring agent which is used as a feed additive in aquaculture nutrition. Recently, potential health benefits of astaxanthin have been discussed which may be partly related to its free radical scavenging and antioxidant properties. Our electron spin resonance (ESR) and spin trapping data suggest that synthetic astaxanthin is a potent free radical scavenger in terms of diphenylpicryl-hydrazyl (DPPH) and galvinoxyl free radicals. Furthermore, astaxanthin dose-dependently quenched singlet oxygen as determined by photon counting. In addition to free radical scavenging and singlet oxygen quenching properties, astaxanthin induced the antioxidant enzyme paroxoanase-1, enhanced glutathione concentrations and prevented lipid peroxidation in cultured hepatocytes. Present results suggest that, beyond its coloring properties, synthetic astaxanthin exhibits free radical scavenging, singlet oxygen quenching, and antioxidant activities which could probably positively affect animal and human health.

Plasma markers of oxidative stress are uncorrelated in a wild mammal

Oxidative stress, which results from an imbalance between the production of potentially damaging reactive oxygen species versus antioxidant defenses and repair mechanisms, has been proposed as an important mediator of life‐history trade‐offs. A plethora of biomarkers associated with oxidative stress exist, but few ecological studies have examined the relationships among different markers in organisms experiencing natural conditions or tested whether those relationships are stable across different environments and demographic groups. It is therefore not clear to what extent studies of different markers can be compared, or whether studies that focus on a single marker can draw general conclusions regarding oxidative stress. We measured widely used markers of oxidative damage (protein carbonyls and malondialdehyde) and antioxidant defense (superoxide dismutase and total antioxidant capacity) from 706 plasma samples collected over a 4‐year period in a wild population of Soay sheep on St Kilda. We quantified the correlation structure among these four markers across the entire sample set and also within separate years, age groups (lambs and adults), and sexes. We found some moderately strong correlations between some pairs of markers when data from all 4 years were pooled. However, these correlations were caused by considerable among‐year variation in mean marker values; correlation coefficients were small and not significantly different from zero after accounting for among‐year variation. Furthermore, within each year, age, and sex subgroup, the pairwise correlation coefficients among the four markers were weak, nonsignificant, and distributed around zero. In addition, principal component analysis confirmed that the four markers represented four independent axes of variation. Our results suggest that plasma markers of oxidative stress may vary dramatically among years, presumably due to environmental conditions, and that this variation can induce population‐level correlations among markers even in the absence of any correlations within contemporaneous subgroups. The absence of any consistent correlations within years or demographic subgroups implies that care must be taken when generalizing from observed relationships with oxidative stress markers, as each marker may reflect different and potentially uncoupled biochemical processes.

Glycosaminoglycan degradation by selected reactive oxygen species

SIGNIFICANCE

Inflammatory diseases (such as arthritis) of the extracellular matrix (ECM) are of considerable socioeconomic significance. There is clear evidence that reactive oxygen species (ROS) and nitrogen species released by, for instance, neutrophils contribute to the degradation of the ECM. Here we will focus on the ROS-induced degradation of the glycosaminoglycans, one important component of the ECM.

RECENT ADVANCES

The recently developed "anti-TNF-α" therapy is primarily directed against neutrophilic granulocytes that are powerful sources of ROS. Therefore, a more detailed look into the mechanisms of the reactions of these ROS is reasonable.

CRITICAL ISSUES

Since both enzymes and ROS contribute to the pathogenesis of inflammatory diseases, it is very difficult to estimate the contributions of the individual species in a complex biological environment. This particularly applies as many products are not stable but only transient products that decompose in a time-dependent manner. Thus, the development of suitable analytical methods as well as the establishment of useful biomarkers is a challenging aspect.

FUTURE DIRECTIONS

If the mechanisms of ECM destruction are understood in more detail, then the development of suitable drugs to treat inflammatory diseases will be hopefully much more successful.

Free radical scavenging and antioxidant activity of betanin: electron spin resonance spectroscopy studies and studies in cultured cells

Betanin is a red pigment present in red beetroot. Recently, potential health benefits of betanin-rich beetroot have been suggested. However, little is known regarding the free radical scavenging and antioxidant activity of betanin. Electron spin resonance spectroscopy (ESR) and spin trapping techniques were applied to evaluate the ability of betanin to scavenge hydroxyl, superoxide, 2,2 diphenyl-1-picrylhydrazyl (DPPH), and galvinoxyl free radicals. In addition, we tested in cultured cells the ability of betanin to prevent DNA damage and to induce the transcription factor Nrf2 (nuclear factor (erythroid-derived 2)-like 2) as well as its down-stream target heme oxygenase1 (HO-1), paraoxonase1 (PON1) and glutathione (GSH). Betanin dose-dependently scavenged DPPH-, galvinoxyl-, superoxide-, and hydroxyl-radicals in the ESR and spin trapping studies and prevented hydrogen peroxide induced DNA damage as determined by the Comet assay. Furthermore, betanin treatment induced the transcription factor Nrf2 and resulted in an increase of HO-1 protein levels, PON1-transactivation and cellular GSH. Present data suggest that betanin is both a free radical scavenger and an inducer of antioxidant defense mechanism in cultured cells.

Oxidative stress and its biomarkers in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease whose etiology remains largely unknown. The uncontrolled oxidative stress in SLE contributes to functional oxidative modifications of cellular protein, lipid and DNA and consequences of oxidative modification play a crucial role in immunomodulation and trigger autoimmunity. Measurements of oxidative modified protein, lipid and DNA in biological samples from SLE patients may assist in the elucidation of the pathophysiological mechanisms of the oxidative stress-related damage, the prediction of disease prognosis and the selection of adequate treatment in the early stage of disease. Application of these biomarkers in disease may indicate the early effectiveness of the therapy. This review is intended to provide an overview of various reactive oxygen species (ROS) formed during the state of disease and their biomarkers linking with disease. The first part of the review presents biochemistry and pathophysiology of ROS and antioxidant system in disease. The second part of the review discusses the recent development of oxidative stress biomarkers that relates pathogenesis in SLE patients and animal model. Finally, this review also describes the reported clinical trials of antioxidant in the disease that have evaluated the efficacy of antioxidant in the management of disease with ongoing conventional therapy.

A fast and validated method for the determination of malondialdehyde in fish liver using high-performance liquid chromatography with a photodiode array detector

Malondialdehyde (MDA) is a biomarker of lipid peroxidation and is present in foods and biological samples such as plasma. A high-performance liquid chromatography (HPLC) method was applied to determine MDA in fish liver samples after derivatization with 2,4-dinitrophenylhydrazine (DNPH) using a ODS2 column (10 cm × 4.6 mm, 3 μm) and a photodiode array detector. The mobile phase consisted of 0.2% acetic acid (v/v) in distilled water and acetonitrile (42:58, v/v). The present method was validated in terms of linearity, lower limit of quantification, lower limit of detection, precision, accuracy, recovery, and stability of MDA according to U.S. Food and Drug Administration (FDA) guidelines. The limit of quantification of MDA was 0.39 μmol/L, which is comparable to other methods. The recovery of the spiked MDA liver samples was in the range of 92.4% to 104.2%. This newly modified HPLC method is specific, sensitive, and accurate and allows the analysis of MDA within 4 min in fish liver but also in other tissues and plasma.

Heat-shock protein 70 is involved in hyperbaric oxygen preconditioning on decompression sickness in rats

Decompression sickness (DCS) is a major concern in diving and space walk. Hyperbaric oxygen (HBO) preconditioning has been proved to enhance tolerance to DCS via nitric oxide. Heat-shock protein (HSP) 70 was also found to have protective effects against DCS. We hypothesized that the beneficial effects of HBO preconditioning on DCS was related to levels of elevated HSP70. HSPs (70, 27 and 90) expressed in tissues of spinal cord and lung in rats was detected at different time points following HBO exposure by Western blot. HSP27 and HSP90 showed a slight but not significant increase after HBO. HSP70 increased and reached highest at 18 h following exposure before decreasing. Then rats were exposed to HBO and subjected to simulated air dive and rapid decompression to induce DCS 18 h after HBO. The severity of DCS, along with levels of HSP70 expression, as well as the extent of oxidative and apoptotic parameters in the lung and spinal cord were compared among different groups of rats pretreated with HBO, HBO plus NG-nitro-l-arginine-methyl ester (l-NAME), HBO plus quercetin or normobaric air. HBO preconditioning significantly reduced the morbidity of DCS (from 66.7% to 36.7%), reduced levels of oxidation (malondialdehyde, 8-hydroxyguanine and hydrogen peroxide) and apoptosis (caspase-3 and -9 activities and the number of apoptotic cells). l-NAME or quercetin eliminated most of the beneficial effects of HBO on DCS, and counteracted the stimulation of HSP70 by HBO. Bubbles in pulmonary artery were detected using ultrasound imaging to observe the possible effect of HBO preconditioning on DCS bubble formation. The amounts of bubbles in rats pretreated with HBO or air showed no difference. These results suggest that HSP70 was involved in the beneficial effects of HBO on DCS in rats, suspected be by the antioxidation and antiapoptosis effects.

Effect of exercise on oxidative stress biomarkers

Acute bouts of aerobic and anaerobic exercise can induce a state of oxidative stress, as indicated by an increase in oxidized molecules in a variety of tissues and body fluids. The extent of oxidation is dependent on the exercise mode, intensity, and duration, and is specifically related to the degree of oxidant production. Findings of increased oxidative stress have been reported for both healthy and diseased subjects following single bouts of exercise. While acute exercise has the ability to induce an oxidative stress, this same exercise stimulus appears necessary to allow for an upregulation in endogenous antioxidant defenses. This chapter presents a summary of exercise-induced oxidative stress.

Role of Oxidative Stress in Peroxisome Proliferator-Mediated Carcinogenesis

In this review, the evidence about the role of oxidative stress in the induction of hepatocellular carcinomas by peroxisome proliferators is examined. The activation of PPAR-alpha by peroxisome proliferators in rats and mice may produce oxidative stress, due to the induction of enzymes like fatty acyl coenzyme A (CoA) oxidase (AOX) and cytochrome P-450 4A1. The effect of peroxisome proliferators on the antioxidant defense system is reviewed, as is the effect on endpoints resulting from oxidative stress that may be important in carcinogenesis, such as lipid peroxidation, oxidative DNA damage, and transcription factor activation. Peroxisome proliferators clearly inhibit several enzymes in the antioxidant defense system, but studies examining effects on lipid peroxidation and oxidative DNA damage are conflicting. There is a profound species difference in the induction of hepatocellular carcinomas by peroxisome proliferators, with rats and mice being sensitive, whereas species such as nonhuman primates and guinea pigs are not susceptible to the effects of peroxisome proliferators. The possible role of oxidative stress in these species differences is also reviewed. Overall, peroxisome proliferators produce changes in oxidative stress, but whether these changes are important in the carcinogenic process is not clear at this time.

Oxidative stress : relationship with exercise and training

Free radicals are reactive compounds that are naturally produced in the human body. They can exert positive effects (e.g. on the immune system) or negative effects (e.g. lipids, proteins or DNA oxidation). To limit these harmful effects, an organism requires complex protection - the antioxidant system. This system consists of antioxidant enzymes (catalase, glutathione peroxidase, superoxide dismutase) and non-enzymatic antioxidants (e.g. vitamin E [tocopherol], vitamin A [retinol], vitamin C [ascorbic acid], glutathione and uric acid). An imbalance between free radical production and antioxidant defence leads to an oxidative stress state, which may be involved in aging processes and even in some pathology (e.g. cancer and Parkinson's disease). Physical exercise also increases oxidative stress and causes disruptions of the homeostasis. Training can have positive or negative effects on oxidative stress depending on training load, training specificity and the basal level of training. Moreover, oxidative stress seems to be involved in muscular fatigue and may lead to overtraining.

Regulation of the Aldo-Keto Reductase Gene akr1b7 by the Nuclear Oxysterol Receptor LXRα (Liver X Receptor-α) in the Mouse Intestine: Putative Role of LXRs in Lipid Detoxification Processes

Liver X receptors (LXRs) regulate the expression of a number of genes involved in cholesterol and lipid metabolism after activation by their cognate oxysterol ligands. AKR1-B7 (aldo-keto reductase 1-B7) is expressed in LXR target tissues such as intestine, and because of its known role in detoxifying lipid peroxides, we investigated whether the AKR1-B7 detoxification pathway was regulated by LXRs. Here we show that synthetic LXR agonists increase the accumulation of AKR1-B7 mRNA and protein levels in mouse intestine in wild-type but not lxr−/− mice. Regulation of akr1b7 by retinoic X receptor/LXR heterodimers is dependent on three response elements in the proximal murine akr1b7 promoter. Two of these cis-acting elements are specific for regulation by the LXRα isoform. In addition, in duodenum of wild-type mice fed a synthetic LXR agonist, we observed an LXR-dependent decrease in lipid peroxidation. Our results demonstrate that akr1b7 is a direct target of LXRs throughout the small intestine, and that LXR activation plays a protective role by decreasing the deleterious effects of lipid peroxides in duodenum. Taken together, these data suggest a new role for LXRs in lipid detoxification.

Free radical mediated peroxidative damage in systemic lupus erythematosus

Free radicals and damage caused by these molecular species are implicated in the pathogenesis of a variety of diseases, including autoimmune. Here we have examined oxidative damage, SOD activity and autoantibodies against SOD in systemic lupus erythematosus (SLE), a multifactorial disease with autoantibody production as an universal feature. We found significantly increased amounts of conjugated dienes in the SLE patients compared to normals (mean value of 0.917 vs 0.627, p = 0.0001) and MDA formation (6.96 vs 4.17 nmoles/microl, p = 0.0006) as well as decreased SOD activity. In addition, we found autoantibodies binding SOD by both ELISA and immunoblot. The presence of anti-SOD antibodies was associated with increased free radical damage in SLE patients. Heat inactivated anti-SOD autoantibodies were able to inhibit the activity of the enzyme. We propose that the inhibition of SOD by autoantibodies is, in part, responsible for the increased free radical damage seen in the disease.

Quantification of 8-iso-prostaglandin-F(2alpha) and 2,3-dinor-8-iso-prostaglandin-F(2alpha) in human urine using liquid chromatography-tandem mass spectrometry

Quantification of 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)) has been suggested to be a reliable indicator of lipid peroxidation that may be related to in vivo free radical generation, oxidative damage, and antioxidant deficiency. We have developed a LC-MS/MS method to quantify 8-iso- PGF(2alpha) and its dinor metabolite, 2,3-dinor-8-iso-prostaglandin F(2alpha) (2,3-dinor-8-iso-PGF(2alpha)), in human urine samples. After an initial purification step using an automated C18 solid phase extraction procedure, the urine sample was injected directly into a liquid chromatography (LC) system and detected with tandem mass spectrometry. The detection limit of the assay was 9 pg for 8-iso-PGF(2alpha) and 3 pg for 2,3-dinor-8-iso-PGF(2alpha) with both inter- and intraday variations of less than 12%. The inaccuracies were less than 3% for both analytes at three different levels. The urinary excretion rate of 2,3-dinor-8-iso-PGF(2alpha) was higher than that of 8-iso-PGF(2alpha), and changed in proportion to the parent compound (R = 0.70, n = 60). Values obtained with this method showed good linear correlation to duplicate 8-iso-PGF(2alpha) measurements performed with GCMS (R = 0.97, n = 15). The mean excretion rates of 8-iso-PGF(2alpha) and 2,3-dinor-8-iso-PGF(2alpha) were significantly higher in smokers than in nonsmokers (0.53 +/- 0.37 vs. 0.25 +/- 0.15 microg/g creatinine, p = 0.002 for 8-iso-PGF(2alpha) and 8.9 +/- 3.8 vs. 4.6 +/- 2.6 microg/g creatinine, p = 0.003 for 2,3-dinor-8-iso-PGF(2alpha), respectively). The excellent accuracy, reproducibility, and high throughput of this method should permit it to be used in large clinical studies and standard clinical laboratories.

Pharmaco-redox regulation of cytokine-related pathways: from receptor signaling to pharmacogenomics

Cytokines represent a multi-diverse family of polypeptide regulators; they are relatively low molecular weight (< 30 kDa), pharmacologically active proteins that are secreted by one cell for the purpose of altering either its own functions (autocrine effect) or those of adjacent cells (paracrine effect). Cytokines are small, nonenzymatic glycoproteins whose actions are both diverse and overlapping (specificity/redundancy) and may affect diverse and overlapping target cell populations. In many instances, individual cytokines have multiple biological activities. Different cytokines can also have the same activity, which provides for functional redundancy (network) within the inflammatory and immune systems. As biological cofactors that are released by specific cells, cytokines have specific effects on cell-cell interaction, communication, and behavior of other cells. As a result, it is infrequent that loss or neutralization of one cytokine will markedly interfere with either of these systems. The biological effect of one cytokine is often modified or augmented by another. Because an interdigitating, redundant network of cytokines is involved in the production of most biological effects, both under physiologic and pathologic conditions, it usually requires more than a single defect in the network to alter drastically the outcome of the process. This fact, therefore, may have crucial significance in the development of therapeutic strategies for biopharmacologic intervention in cytokine-mediated inflammatory processes and infections.

C11-BODIPY(581/591), an oxidation-sensitive fluorescent lipid peroxidation probe: (micro)spectroscopic characterization and validation of methodology

C11-BODIPY(581/591) is a fluorescent radio-probe for indexing lipid peroxidation and antioxidant efficacy in model membrane systems and living cells, with excellent characteristics: (i) emission in the visible range of the electromagnetic spectrum, with good spectral separation of the nonoxidized (595 nm) and oxidized (520 nm) forms; (ii) has a high quantum yield and because of this, low labeling concentrations can be used, ensuring minimal perturbation of the membrane whilst retaining favorable signal to noise ratios; (iii) has a good photo-stability and displays very few fluorescence artifacts; (iv) is virtually insensitive to environmental changes, i.e., pH or solvent polarity; (v) is lipophilic and as such easily enters membranes; (vi) once oxidized, C11-BODIPY(581/591) remains lipophilic and does not spontaneously leave the lipid bilayer; (vii) C11-BODIPY(581/591) localizes in two distinct pools within the lipid bilayer, a shallow pool at 18 A and a deep pool at < 7.5 A from the center of the bilayer; (viii) is not cytotoxic to rat-1 fibroblasts up to 50 microM; (ix) is sensitive to a variety of oxy-radicals and peroxynitrite, but not to superoxide, nitric oxide, transition metal ions, and hydroperoxides per se; (x) its sensitivity to oxidation is comparable to that of endogenous fatty acyl moieties.

Investigation of tyrosine nitration in proteins by mass spectrometry

In vivo nitration of tyrosine residues is a post-translational modification mediated by peroxynitrite that may be involved in a number of diseases. The aim of this study was to evaluate possibilities for site-specific detection of tyrosine nitration by mass spectrometry. Angiotensin II and bovine serum albumin (BSA) nitrated with tetranitromethane (TNM) were used as model compounds. Three strategies were investigated: (i) analysis of single peptides and protein digests by matrix-assisted laser desorption/ionization (MALDI) peptide mass mapping, (ii) peptide mass mapping by electrospray ionization (ESI) mass spectrometry and (iii) screening for nitration by selective detection of the immonium ion of nitrotyrosine by precursor ion scanning with subsequent sequencing of the modified peptides. The MALDI time-of-flight mass spectrum of nitrated angiotensin II showed an unexpected prompt fragmentation involving the nitro group, in contrast to ESI-MS, where no fragmentation of nitrated angiotensin II was observed. The ESI mass spectra showed that mono- and dinitrated angiotensin II were obtained after treatment with TNM. ESI-MS/MS revealed that the mononitrated angiotensin II was nitrated on the side-chain of tyrosine. The dinitrated angiotensin II contained two nitro groups on the tyrosine residue. Nitration of BSA was confirmed by Western blotting with an antibody against nitrotyrosine and the sites for nitration were investigated by peptide mass mapping after in-gel digestion. Direct mass mapping by ESI revealed that two peptides were nitrated. Precursor ion scanning for the immonium ion for nitrotyrosine revealed two additional partially nitrated peptides. Based on the studies with the two model compounds, we suggest that the investigation of in vivo nitration of tyrosine and identification of nitrated peptides might be performed by precursor ion scanning for the specific immonium ion at m/z 181.06 combined with ESI-MS/MS for identification of the specific nitration sites.

Induction of urinary excretion of 3-nitrotyrosine, a marker of oxidative stress, following administration of pyridostigmine bromide, DEET (N,N-diethyl-m-toluamide) and permethrin, alone and in combination in rats

In this study, we determined levels of 3-nitrotyrosine in rat urine following administration of a single oral dose of 13 mg/kg pyridostigmine bromide (PB) (3-dimethylaminocarbonyloxy-N-methylpyridinum bromide), a single dermal dose of 400 mg/kg N,N-diethyl-m-toluamide (DEET) and a single dermal dose of 1.3 mg/kg permethrin, alone and in combination. Urine samples were collected from five treated and five control rats at 4, 8, 16, 24, 48, and 72 h following dosing. Solid-phase extraction coupled with high-performance liquid chromatography with ultraviolet detection at 274 nm was used for the determination of tyrosine and 3-nitrotyrosine. A single oral dose of PB and a single dermal dose of DEET or their combination significantly (P<0.05) increased levels of 3-nitrotyrosine starting 24 h after dosing compared with control urine samples. The maximum increase of 3-nitroytyrosine was detected 48 h after combined administration of PB and DEET. The ratio of 3-nitrotyrosine to tyrosine in urine excreted 48 h after dosing was 0.19+/-0.04, 0.20+/-0.05, 0.28+/-0.03, 0.32+/-0.04, 0.19+/-0.05, 0.42+/-0.04, 0.27+/-0.03, 0.36+/-0.04, and 0.48+/-0.04 following administration of water, ethanol, PB, DEET, permethrin, PB+DEET, PB+permethrin, DEET+permethrin, and PB+DEET+permethrin, respectively. The results indicate that an oral dose of PB and a dermal administration of DEET, alone and in combination, could generate free radical species, and thus increase levels of 3-nitrotyrosine in rat urine. Induction of 3-nitrotyrosine, a marker of oxidative stress, following exposure to these compounds could be significant in understanding the proposed enhanced toxicity following combined exposure to these compounds.

Biomarkers of oxidative stress: an analytical approach

Oxidative stress is implicated in many pathological processes and results from a disruption of the prooxidant/antioxidant balance. This review will focus on noninvasive biomarkers of radical-induced damage in biological fluids and particularly in blood. Special attention will be addressed to new analytical methods for the measurement of radical-mediated alterations in the integrity of lipids, proteins and DNA.