Reducing equivalents in the aging process

Cyclic Voltammetry in Biological Samples: A Systematic Review of Methods and Techniques Applicable to Clinical Settings

Oxidative stress plays a pivotal role in the pathogenesis of many diseases, but there is no accurate measurement of oxidative stress or antioxidants that has utility in the clinical setting. Cyclic Voltammetry is an electrochemical technique that has been widely used for analyzing redox status in industrial and research settings. It has also recently been applied to assess the antioxidant status of in vivo biological samples. This systematic review identified 38 studies that used cyclic voltammetry to determine the change in antioxidant status in humans and animals. It focusses on the methods for sample preparation, processing and storage, experimental setup and techniques used to identify the antioxidants responsible for the voltammetric peaks. The aim is to provide key information to those intending to use cyclic voltammetry to measure antioxidants in biological samples in a clinical setting.

Antioxidants in dermatology

The skin cells continuously produce, through cellular respiration, metabolic processes or under external aggressions, highly reactive molecules oxidation products, generally called free radicals. These molecules are immediately neutralized by enzymatic and non-enzymatic systems in a physiological and dynamic balance. In situations where this balance is broken, various cellular structures, such as the cell membrane, nuclear or mitochondrial DNA may suffer structural modifications, triggering or worsening skin diseases. several substances with alleged antioxidant effects has been offered for topical or oral use, but little is known about their safety, possible associations and especially their mechanism of action. The management of topical and oral antioxidants can help dermatologist to intervene in the oxidative processes safely and effectively, since they know the mechanisms, limitations and potential risks of using these molecules as well as the potential benefits of available associations.

A hydrazine coupled cycling assay validates the decrease in redox ratio under starvation in Drosophila

A commonly used enzymatic recycling assay for pyridine nucleotides has been adapted to directly measure the NAD⁺/NADH redox ratio in Drosophila melanogaster. This method is also suitable for quantification of NADP⁺ and NADPH. The addition of a coupling reaction removing acetaldehyde produced from the alcohol dehydrogenase (ADH) reaction was shown to improve the linearity of NAD(H) assay. The advantages of this assay method are that it allows the determination of both NAD⁺ and NADH simultaneously while keeping enzymatic degradation of pyridine nucleotides minimal and also achieving better sensitivity. This method was used to determine the redox ratio of D. melanogaster and validated substantial decrease of redox ratio during starvation.

Non-invasive evaluation of skin cytokines secretion: an innovative complementary method for monitoring skin disorders

In this review, a novel non-invasive approach based on skin surface wash sampling is described. Since the epidermis possesses a high metabolic activity, the secretion of various biomarkers can be exploited to develop non-invasive procedures for skin measurement to monitor disorders and to define a therapeutic strategy. Thus, we developed a method for the quantification of skin surface compounds. In this procedure, a well is placed on skin surface and is attached using an adhesive pad. Extraction buffer is introduced into the well for 30 min incubation period and the secretion of different biomarkers on skin surface can be measured: cytokines, antioxidants, peptides, RNA, DNA volatile organic compounds etc. Here, the focus is on cytokine measurement. After collecting skin samples cytokines can be quantified using ELISA assay. Since so far cytokine levels in skin have been evaluated mostly by invasive and prolonged procedures (punch biopsy, blister fluid and scrapping), employing this method has important implications, because it allows assessing cytokine amount with minimal invasion and high accuracy. We have already applied skin surface wash sampling for cytokine quantification in different clinical conditions: psoriasis, atopic dermatitis and chronic renal failure. A distinct pattern of cytokine secretion has been demonstrated for each disorder. Differences were also observed between lesional and non-lesional areas. The obtained results shed a new light on cutaneous cytokine expression in different clinical conditions. Moreover, the interplay between cytokines and other soluble compounds can give an added value in understanding the mechanism of skin pathologies.

Ginkgo biloba (EGb 761) extract: effects on the myenteric plexus of the large intestine in Wistar rats

The objective of this study was to evaluate the effect of the purified extract of the Ginkgo biloba (EGb 761) plant on the myenteric plexus in the proximal and distal colon of Wistar rats for a period of 120 days. The experimental rats were divided into two age groups: a young group, sacrificed at age 90 days, and an adult group, sacrificed at age 210 days. We observed a significant reduction in the number of neurons in the myenteric plexus of the adult group compared to the young group in both of the segments studied (P < 0.01). The adult group treated with Ginkgo biloba showed a significant increase in neuronal profile area in both the segments studied (P < 0.001). It can be concluded from these results that treatment with the purified Ginkgo biloba (EGb 761) plant extract at a dose of 50 mg/kg body weight has neurotrophic effect on the myenteric plexus in the proximal and distal colon of rats after 120 days of treatment.

Antioxidant peptidomics reveals novel skin antioxidant system

It is generally agreed that reactive oxygen species (ROS) contribute to skin aging, skin disorders, and skin diseases. Skin possesses an extremely efficient antioxidant system. This antioxidant activity is conferred by two systems: antioxidant enzymes and small molecules that can scavenge ROS by donating electrons. No gene-encoded secreted ROS scavengers have been reported. Amphibian skin is a multifunctional organ acting in defense, respiration, and water regulation, although it seems susceptible. Amphibian skins are easily harmed by biological or non-biological attacks such as microorganism infection or radiation injury. Among vertebrates, skins of amphibian are exposed to more dangers of radiation injury than others. Radiation toxicity occurs by directly attacking the genetic material and/or by generating ROS. In addition, amphibian skin respiration and inflammatory response also induce ROS generation. It is rational to hypothesize that amphibian skins should have potent free radical scavenging and radioprotective ability for their survival. Rana pleuraden is distributed in Southwest of China; it lives in the subtropical plateau (altitude around 2300 m) where there is strong ultraviolet radiation and long duration of sunshine. By peptidomics and genomics approaches, a large amount of antioxidant peptides belonging to 11 different groups with variable structures were isolated from the skin secretions of R. pleuraden. Their free radical scavenging and anti-inflammatory abilities were studied. All of these peptide share highly homologous preproregions, although mature antioxidant peptides have very divergent primary structures, suggesting the possibility of a common ancestor. Some peptides were also found to have multifunctional properties, such as combined antioxidant, anti-inflammatory, and antimicrobial activities. According to our knowledge, no gene-encoded specific antioxidant peptides have been reported except metallothionein. Our work possibly reveals a new skin antioxidant system. The current work also provides a large amount of peptide candidates with medical-pharmaceutical significance.

The antioxidant tempamine: in vitro antitumor and neuroprotective effects and optimization of liposomal encapsulation and release

The piperidine nitroxide tempamine (TMN) is a cell-permeable, stable radical having antioxidant, anticancer, and proapoptotic and/or pronecrotic activities, as was demonstrated by us in cell cultures. We also demonstrated synergism between TMN and doxorubicin in doxorubicin-sensitive and doxorubicin-resistant cell lines. Treatment of the C26 mouse colon carcinoma model in vivo also demonstrated synergism between TMN and doxorubicin in sterically stabilized liposomes (SSLs) containing TMN (SSL-TMN) and those containing doxorubicin. The above effects of TMN and SSL-TMN motivated us to develop and optimize the SSL-TMN formulation so that it will be able to reach the disease site with a sufficiently high TMN level and a release rate needed to achieve a therapeutic effect. Because TMN is an amphipathic weak base, it was remote loaded by an intraliposome high/extraliposome low transmembrane ammonium sulfate gradient. The kinetics and level of TMN loading were monitored by cyclic voltammetry (CV) and electron paramagnetic resonance (EPR); the latter also indicates TMN precipitation in the intraliposomal aqueous phase. The regeneration of the original CV and EPR signals by the ionophore nigericin indicates that TMN remained fully intact during loading and release. The cardinal role of the transmembrane ammonium ion gradient in the loading process was proven by the use of the selective ionophores nonactin (for NH4+) and nigericin (for H+). The anion of the ammonium salts affects loading stability and the rate of TMN release, both mediated through the TMN state of aggregation in the intraliposomal aqueous phase. The greater the TMN salt precipitation, the slower the TMN release rate. This was supported by measurement of osmolality, which is inversely related to TMN salt precipitate. Precipitation is in the order SO4(-2)>Cl-1>glucuronate-1. Liposome lipid composition, magnitude of the transmembrane ammonium ion gradient, and type of anion of the ammonium salt determine the amount of TMN loaded and its release rate.

Antioxidant vitamins E and C as adjunct therapy of severe acute lower-respiratory infection in infants and young children: a randomized controlled trial

OBJECTIVE

To evaluate the effect of antioxidant Vitamins E and C as adjunct therapy of severe acute lower respiratory infection (ALRI) in children.

DESIGN

Randomized double-blind placebo-controlled clinical trial.

SETTING

A large childrens' hospital serving the urban poor in Kolkata, India.

SUBJECTS

Children aged 2-35 months admitted with severe ALRI.

INTERVENTION

In total, 174 children were randomly assigned to receive alpha-tocopherol 200 mg and ascorbic acid 100 mg twice daily or placebo for 5 days. All children received standard treatment for severe ALRI. Outcome measures were: time taken to recover from a very ill status, fever, tachypnoea, and feeding difficulty; and improvement in oxidative stress and immune response indicated by thiobarbituric acid reacting substances (TBARS) and response to skin antigens, respectively.

RESULTS

Recovery rate ratios (95% CI) using proportional hazards model were 0.89 (0.64-1.25), 1.01 (0.72-1.41), 0.86 (0.57-1.29), and 1.12 (0.77-1.64) for very ill status, feeding difficulty, fever, and tachypnoea, respectively. TBARS values were high and similar in the two groups at admission, discharge, and at 2 weeks follow-up. Serum alpha-tocopherol significantly increased in treated group at discharge. Immune response to skin antigens were very poor at admission and after 2 weeks, in both groups.

CONCLUSION

Infants with severe ALRI failed to benefit from two antioxidant nutrients as adjunct therapy. Severe ALRI in infants may cause cell-mediated immune dysfunction. We need a better understanding of oxidative processes in growing infants to help us better design interventions with antioxidant therapy.

Total antioxidant capacity is impaired in different structures from aged rat brain

Our data support a disproportion between free radicals levels and scavenging systems activity in different cerebral regions of the aging rat. We investigated the total reactive antioxidant potential and reactivity levels, which represent the total antioxidant capacity, in different cerebral regions of the aging rat (cortex, striatum, hippocampus and the cerebellum). In addition, we have determined several oxidative stress parameters, specifically the free radicals levels, the macromolecules damage (lipid peroxidation and carbonyl content), as well as the antioxidant enzymes activities in different cerebral areas from young (2 months-old), mature adult (6 months-old) and old (24 months-old) male Wistar rats. Free radicals levels, determined by 2',7'-dichlorofluorescein diacetate probe, were higher in striatum, cerebellum and hippocampus from aged rats. There was an age-related increase in lipoperoxidation in hippocampus and cerebral cortex. In the cerebellum, a high activity of superoxide dismutase and a decrease of catalase activity were observed. The striatum exhibited a significant catalase activity decrease; and glutathione peroxidase activity was diminished in the hippocampus of mature and aged rats. There was a marked decrease of total antioxidant capacity in hippocampus in both reactivity and potential levels, whereas striatum and cerebral cortex displayed a reduction on reactivity assay. We suggest that age-related variations of total antioxidant defenses in brain may predispose structures to oxidative stress-related neurodegenerative disorders.

Changes in reducing power profile of gastric juice in patients with active duodenal ulcer

Reactive oxygen species have been postulated to play a role in the pathogenesis of mucosal GI injury and in peptic ulcer disease (PUD). The low molecular weight antioxidants (LMWA) group plays an important role in the defense mechanism of the GI tract against oxidative damage, and is a major component of the reducing capacity of biological tissues and fluids. We hypothesized that altered gastric LMWA anti oxidative status might play a role in the pathogenesis of upper GI disorders such as PUD and could be evaluated by measuring gastric juice reducing power. The aim of the present study was to determine, by cyclic voltammetry, changes in the overall antioxidant activity of the gastric juice in active duodenal ulcer (DU) obtained during upper endoscopy from patients as compared with normal subjects. The results show that in 28/37 (76%) of the control subjects, gastric juice demonstrated a reducing power of at least two anodic waves indicating at least two different LMWA groups. Three or more anodic waves were recorded in 12 normal subject (32%). In contrast, 16/25 (64%) of gastric juice samples obtained from active DU patients exhibited only one anodic wave usually at a high potential (>900 mV). These results imply that gastric juice normally possesses a reducing power profile that can be determined by cyclic voltammetry. This profile is significantly changed in untreated DU disease. These changes in active DU may indicate decreased gastric antioxidant activity reflecting reduced mucosal protection that leading to increased susceptibility of the gastro-duodenum to injury.

Age-Dependent Change of Uric Acid Level in the Dermis Using Cutaneous Microdialysis

BACKGROUND

We had proposed the usefulness of cutaneous microdialysis for the study of antioxidants in the skin.

OBJECTIVE

We designed a study analyzing the level of uric acid in the skin, one of the major antioxidants, for an age-dependent change.

METHODS

16 healthy male volunteers were divided into two groups according to age. Eleven subjects were in their 3rd decade, under 30 years of age (young group) and the others were their 8th decade (old group), over 70 years of age. Dialysate samples were analyzed using high-performance liquid chromatography analysis.

RESULTS

In the young group the mean level of uric acid was 31.9+/-16.1 microg/ml, while in old group it was 13.4+/-5.2 microg/ml.

CONCLUSION

This result demonstrated an in vivo state of antioxidant level in the human skin and the age-dependent difference was concordant with other in vitro or ex vivo studies; therefore, cutaneous microdialysis could be used in analysis and monitoring studies including human antioxidants and anti-aging.

Oxidative stress in childhood—in health and disease states

The accumulated information concerning the involvement of reactive oxygen species in many clinical disorders and disease states has led to the potential for intervention with antioxidants in these cases. There are currently numerous clinical trials involving administration of antioxidants in a variety of conditions such as coronary heart disease, cataract, cancer and neurodegenerative diseases. At the same time therapeutic trials aimed at preventing and delaying the aging process are also under investigation. Numerous disorders, in childhood, have also been linked to oxidative damage. The aim of this review is to provide an overview of oxidative stress, its mechanisms, targets and damage incurred, as pertaining specifically to clinical disorders during childhood. The defense mechanisms against oxidation; the enzymatic antioxidants and low molecular weight antioxidants are defined and a number of methods commonly used for evaluation of oxidative stress (methods for measurement of lipid and protein oxidation end products and methods for measurement of antioxidant defense capacity) described. Specific diseases related to oxidative stress in infancy and childhood are reviewed and the possible effect of nutritional intake on oxidative stress in the healthy child discussed. Other issues addressed include the ability of oxidative stress, as measured in plasma to reflect intratissue oxidation, the need for a simple laboratory method for characterization of an oxidative stress 'profile', the proposed role of oxidative stress in biological processes pertaining to growth and maturation and possible implications of unrestricted antioxidant supplementation.

Low molecular weight antioxidants released from the skin's epidermal layers: an age dependent phenomenon in the rat

Skin is one of the tissues most exposed to oxidative stress both from endogenous and exogenous sources. Therefore, it can be speculated that skin possesses an extremely efficient antioxidant defense mechanism, particularly in its epidermal layers. The present study shows that human and rat skins possess different and unique reducing antioxidant profiles. These reducing antioxidants can be washed out into the surrounding environment. Non-invasive measurements indicated that skin releases low molecular weight antioxidants (LMWA) from its epidermal layers. Cyclic voltammetry measurements have shown that rat skin releases three major groups of reducing antioxidants at peak potentials of 476 and 889 and 1044 mV while human skin releases two major groups at peak potentials of 779 and 1068 mV. In rat, the overall concentrations of the LMWA secreted decreased significantly with age. The major components of the LMWA composing the first anodic wave in rats were identified as uric acid and ascorbic acid. Uric acid and other as yet uncharacterized LMWA, but not ascorbic acid, were released in human skin. Differences in the ability to release high levels of uric acid among species were well correlated with their metabolic rates. It is suggested that in rat the released LMWA may serve as a possible marker for aging of the skin.

Iron and ascorbic acid concentrations in human dermis with regard to age and body sites

BACKGROUND

Reactive oxygen species (ROS) contribute to processes relating to cutaneous aging. Iron catalyses ROS formation whereas ascorbic acid (AA) plays a fundamental role in defending the organism against undesirable ROS action.

OBJECTIVE

The aim of this work was to determine the ex vivo iron and AA concentrations in human dermis from different age groups to better understand their role.

METHODS

Skin fragments were collected from 66 female patients during surgical operations and were grouped according to age: group I (<15 years, before puberty, n = 12), group II (15-50 years, adults, n = 42), and group III (>50 years, advanced age adults, n = 12). Two sites were investigated: the abdomen (unexposed areas) and face (exposed sites). Iron and AA were collected from human dermis by microdialysis and assessed by atomic absorption spectrometry and gas chromatography mass spectrometry, respectively.

RESULTS

Iron concentrations in the dermis were significantly higher in group III (27.4 +/- 20.9 microg/l) than in group I (13.8 +/- 3.3 microg/l; p< 0.05 ). An inverse correlation between AA dermis levels and increasing age was detected. For groups III and I, iron and AA concentrations were significantly different in dermis from the face compared to that of the abdomen (p < 0.05).

CONCLUSION

This study shows for the first time that there is a direct relationship between iron and AA concentrations in the dermis and aging. Moreover, iron and AA concentrations differed according to body site.

Oxidation of biological systems: oxidative stress phenomena, antioxidants, redox reactions, and methods for their quantification

Reactive oxygen species (ROS) and other radicals are involved in a variety of biological phenomena, such as mutation, carcinogenesis, degenerative and other diseases, inflammation, aging, and development. ROS are well recognized for playing a dual role as deleterious and beneficial species. The objectives of this review are to describe oxidative stress phenomena, terminology, definitions, and basic chemical characteristics of the species involved; examine the biological targets susceptible to oxidation and the defense mechanisms of the organism against these reactive metabolites; and analyze methodologies, including immunohistochemical markers, used in toxicological pathology in the visualization of oxidative stress phenomena. Direct detection of ROS and other free radicals is difficult, because these molecules are short-lived and highly reactive in a nonspecific manner. Ongoing oxidative damage is, thus, generally analyzed by measurement of secondary products including derivatives of amino acids, nuclei acids, and lipid peroxidation. Attention has been focused on electrochemical methods based on voltammetry measurements for evaluating the total reducing power of biological fluids and tissues. This approach can function as a tool to assess the antioxidant-reducing profile of a biological site and follow changes in pathological situations. This review thus includes different topics essential for understanding oxidative stress phenomena and provides tools for those intending to conduct study and research in this field.

Vitamins C and E improve rat embryonic antioxidant defense mechanism in diabetic culture medium

BACKGROUND

Diabetes teratogenicity seems to be related to embryonic oxidative stress and the extent of the embryonic damage can apparently be reduced by antioxidants. We have studied the mechanism by which antioxidants, such as vitamins C and E, reduce diabetes-induced embryonic damage. We therefore compared the antioxidant capacity of 10.5-day-old rat embryos and their yolk sacs cultured for 28h in diabetic culture medium with or without vitamins C and E.

METHODS

The embryos were cultured in 90% rat serum to which 2mg/ml glucose, 2mg/ml beta hydroxy butyrate (BHOB) and 10 microg/ml of acetoacetate were added. Rat embryos were also cultured in a diabetic medium with 25 microg/ml of vitamin E and 50 microg/ml of vitamin C. Control embryos were cultured in normal rat serum with or without vitamins C and E.

RESULTS

Decreased activity of Cu/Zn superoxide dismutase (SOD) and of catalase (CAT) in the "diabetic" embryos and their yolk sacs, and reduced concentrations of low molecular weight antioxidant (LMWA) were found. Under these conditions we also found a decrease in vitamin C and vitamin E concentrations in the embryos, as measured by HPLC. In situ hybridization for SOD mRNA showed a marked reduction of SOD mRNA in the brain, spinal cord, heart and liver of embryos cultured in diabetic medium in comparison to controls. Following the addition of vitamins C and E to the diabetic culture medium, SOD and CAT activity, the concentrations of LMWA, the levels of vitamin C and E and the expression of SOD mRNA in the embryos and yolk sacs returned to normal.

CONCLUSIONS

Diabetic metabolic factors seem to have a direct effect on embryonic SOD gene and perhaps genes of other antioxidant enzymes, reducing embryonic endogenous antioxidant defense mechanism. This in turn may cause a depletion of the LMWA, such as vitamins C and E. The addition of these vitamins normalizes the embryonic antioxidant defense mechanism, reducing the damage caused by the diabetic environment.

Neurological recovery from closed head injury is impaired in diabetic rats

Diabetes mellitus is a metabolic disorder associated with central nervous system impairments. Recent studies implicate oxidative stress mediated by reactive oxygen species (ROS) in the pathogenesis of diabetic complications. ROS have been shown to play role in the pathophysiology of brain injury. In the present study, closed head injury (CHI) was induced in diabetic rats to test the hypothesis that chronic oxidative stress exacerbates brain damage following CHI. Neurological recovery, edema, levels of low molecular weight antioxidants (LMWA), and markers of lipid peroxidation were determined at different intervals after injury. Diabetic rats (4 weeks after induction with streptozotocin) were subjected to CHI. Brain edema (percent water) and clinical status (neurological severity score) were assessed during 7 days. Brain LMWA were determined using cyclic voltammetry (CV) and HPLC-EC. In addition, conjugated dienes and thiobarbituric acid reactive substances (TBARS) were measured. Diabetic-CHI rats exhibited a lower rate of recovery and greater and more sustained edema (p < 0.01), as compared with the controls. At all times diabetic rats had higher levels of TBARS and conjugated dienes and lower concentrations of LMWA, and of vitamins C and E, suggesting chronic oxidative stress. At 5 min of CHI, the amounts of LMWA in control-CHI brains decreased (approximately 50%, p < 0.01) and returned to normal by 48 h and 7 days. In the diabetic-CHI brain only one class of LMWA slightly declined but remained low for 7 days. The present results support the hypothesis that diabetic rats are under chronic oxidative stress, and suffer greater neurological dysfunction, associated with further lipid peroxidation following CHI.

Atmospheric oxygen accelerates the induction of a post-mitotic phenotype in human dermal fibroblasts: the key protective role of glutathione

It has been proposed that ageing of human dermal fibroblasts occurs as a multi-stage process during which cells progress from a mitotic to a post-mitotic state. We describe the development of a simple and novel cell-cloning model for identifying and quantifying the different fibroblast morphotypes associated with the induction of post mitotic behaviour. We have found that under atmospheric (20%) oxygen tension a significant proportion of human dermal fibroblasts are rapidly induced to switch from a mitotic to a post-mitotic phenotype. In contrast, under more physiological (4%) oxygen conditions, the induction of a post-mitotic phenotype is largely prevented. Increasing oxidative stress by addition of hydrogen peroxide or depletion of glutathione also induced a switch from a mitotic to a post-mitotic phenotype in these cells, whereas addition of the anti-oxidant N-acetylcysteine under atmospheric (20%) oxygen tension potently inhibited this process. In addition, a statistically significant correlation was observed between the magnitude of intracellular glutathione depletion and the reduction in the population of mitotic cells in this model. We propose that the switch from a mitotic to a post-mitotic phenotype represents a process of cellular ageing and that standard atmospheric oxygen tension imposes a substantial oxidative stress on dermal fibroblasts which accelerates this process in culture. The data also suggest that intracellular glutathione levels strongly influence the induction of a post-mitotic phenotype and that, by implication, depletion of glutathione may play a significant role in the progression of cellular ageing in human skin.

Skin low molecular weight antioxidants and their role in aging and in oxidative stress

The overall skin low molecular weight antioxidant (LMWA) capacity was evaluated during the aging process and following exposure to oxidative stress. Several invasive and non-invasive techniques were developed for evaluating total antioxidant activity. It was found that the skin possesses an extremely efficient and unique antioxidant activity that is better than other tissues. During the aging process a significant decrease in the levels and activity of the water-soluble LMWA was detected while no change and even a slight increase was recorded for the lipophilic LMWA. Similar results were obtained following exposure to oxidative stress. A significant decrease in the water soluble LMWA was recorded in all the stress induced procedures indicating a common mechanism of response. It has also been shown that along with the reduction in total water soluble antioxidant activity there is an accumulation of oxidized adducts. This was observed both on the surface of the skin and in deeper layers. It has been found that skin releases LMWA from its surface. This secretion phenomenon was found to be age dependent. Following exposure to oxidative stress of various kinds, the release of LMWA from the skin was significantly enhanced. This may suggest a physiological mechanism of the skin to cope with oxidative stress, which would open new possibilities for intervention.

Quantification of the overall reactive oxygen species scavenging capacity of biological fluids and tissues

A method has been developed for measuring and evaluating the overall antioxidant activity derived from the low-molecular weight antioxidants (scavengers). The principle governing this method is based on a common chemical characteristic of the scavengers, their reducing properties. It was hypothesized and then demonstrated that an evaluation of the overall reducing power of a biological sample correlates with the overall scavenging activity of the sample. In order to quantify the total reducing power, the cyclic voltammetry methodology was applied. The resulting measurements correlated with the antioxidant activity of both hydrophilic and lipophilic scavengers. The method is suitable for use in biological fluids and in tissue homogenates, and can supply information concerning the type of antioxidants and their total concentration without having to determine specific compounds. A noninvasive procedure for determining skin overall scavenging activity is also described. This method is based on a well containing an extraction solution that is attached to the skin's surface. Following incubation time the extraction solution is analyzed using the cyclic voltammeter instrument and other methods. We have found these methods suitable for evaluating the reducing capacity status in various clinical conditions such as diabetes, ionizing and nonionizing irradiation, brain degenerative diseases, head trauma, and inflammatory bowel diseases. This method is also an efficient tool for evaluating the overall antioxidant capacity of mixtures of antioxidant preparations in vitro. The measurements themselves are simple and rapid. Furthermore, they do not require manipulation of the samples.

Increased hepatic lipid soluble antioxidant capacity as compared to other organs of streptozotocin-induced diabetic rats: a cyclic voltammetry study

It has been suggested that oxidative stress plays an important role in the chronic complications of diabetes. The experimental findings regarding the changes in tissue antioxidant enzymes and lipid peroxidation of diabetic tissues have been inconsistent. Previous studies in our laboratory demonstrated that the reducing power of a specific tissue correlates with its low molecular weight antioxidant (LMWA) capacity. In the present study, the overall LMWA capacity (reducing equivalents) of plasma and tissues of streptozotocin (STZ)-induced diabetic rats (1-4 weeks) and insulin treated diabetic rats were measured by cyclic voltammetry. Levels of water and lipid soluble LMWA capacity progressively decreased in the diabetic plasma, kidney, heart and brain, while the diabetic liver, at 2, 3 and 4 weeks after STZ injection, showed a significant increase in the overall lipid soluble LMWA capacity (p < 0.001). Subsequently, analysis of specific components by high pressure liquid chromatography (electrochemical detection) showed decreased levels of ascorbic acid in plasma, kidney, heart and brain of diabetic animals. The alpha-tocopherol level dropped in all tissues, except for the liver in which there was a significant increase (p < 0.01 and p < 0.001 at 2-4 weeks). Lipid peroxidation was assessed by conjugated diene levels, which increased significantly in all diabetic tissues except the liver. Insulin treatment that was started after 3 weeks of diabetes and continued for 3 weeks showed no change in the conjugated dienes and in the overall LMWA capacity in all organs. Our results suggest a unique behavior of the liver in the STZ-induced diabetic rats to the stress and indicate its higher capacity to cope with oxidative stress as compared to other organs.

Role of reactive oxygen species (ROS) in the diabetes-induced anomalies in rat embryos in vitro: reduction in antioxidant enzymes and low-molecular-weight antioxidants (LMWA) may be the causative factor for increased anomalies

A disturbed embryonic antioxidant defense mechanism may play a major role in diabetes-induced teratogenesis. We therefore studied the antioxidant capacity of 10.5-day-old rat embryos and their yolk sacs after culture for 28 hr in vitro under diabetic conditions (3 mg/ml glucose, 2 mg/ml beta-hydroxybutyrate (BHOB) and 10 microg/ml of acetoacetate), as compared with control embryos in vitro. We found a high rate of congenital anomalies, decreased growth and protein content, and a decrease in the activity of both superoxide dismutase (SOD) and catalase (CAT) under diabetic conditions, as compared with controls. The reducing power, which reflects the concentration and type of water-soluble and of lipid-soluble low-molecular-weight antioxidants (LMWA), was measured by cyclic voltammetry. Generally, LMWA were reduced in the embryos and yolk sacs under diabetic conditions. In the water-soluble fraction of control embryos and yolk sacs, two peak potentials were found, indicating two major groups of LMWA, while only one peak potential was found under diabetic conditions, indicating that an entire group of LMWA is missing. HPLC studies have demonstrated a decrease in vitamin C (water-soluble fraction) and in vitamin E (lipid-soluble fraction) under diabetic culture conditions, and an increase in uric acid. Generally, the concentration of LMWA was higher in the embryos than in the yolk sac. LMWA concentration, protein content, and antioxidant enzyme activity were lower in the malformed experimental embryos than in experimental embryos without anomalies. The addition of vitamins C and E to the diabetic culture medium abolished the deleterious effects of the diabetic serum on the embryos. The disturbed antioxidant defense mechanism under diabetic conditions may be explained, at least in part, by a direct effect of diabetic metabolic factors on the activity of antioxidant enzymes and on the concentration of reducing equivalents. This, in turn, may be embryotoxic.

Skin antioxidants: their role in aging and in oxidative stress--new approaches for their evaluation

Skin is a highly metabolic tissue which possesses the largest surface area in the body and serves as the protective layer for internal organs [1]. Skin is also a major candidate and target of oxidative stress. It is designed to give both physical and biochemical protection, and is equipped with a large number of defense mechanisms. The skin tissue is exposed to a variety of damaging species which originate in the outer environment, in the skin itself, and in various endogenous sources [2, 3]. The structure of skin is quite complex being composed of several layers, each of which plays a specific role and carries out different functions [4]. Each layer is equipped with its own arsenal of defense molecules, and the various systems differ from each other based on the layer's susceptibility to oxidative stress and its function. It is generally agreed that one of the major and important contributions to skin aging, skin disorders and skin diseases results from reactive oxygen species (ROS) [1, 5]. Due to the high occurrence of potential biological targets for oxidative damage, skin is very susceptible to such reactions. For example, skin is rich in lipids, proteins, and DNA, all of which are extremely sensitive to the oxidation process [6-8]. Elucidation of the mechanisms involved in skin oxidation and the examination of the defense systems may contribute to the understanding of skin aging and of the mechanisms involved in the various pathological processes of skin. This review addresses the antioxidant defense mechanism of the skin, the role it plays during the aging process, and the role skin has following exposure to oxidative stresses.

Closed head injury in the rat induces whole body oxidative stress: overall reducing antioxidant profile

Traumatic injury to the brain triggers the accumulation of harmful mediators, including highly toxic reactive oxygen species (ROS). Endogenous defense mechanism against ROS is provided by low molecular weight antioxidants (LMWA), reflected in the reducing power of the tissue, which can be measured by cyclic voltammetry (CV). CV records biological peak potential (type of scavenger), and anodic current intensity (scavenger concentration). The effect of closed head injury (CHI) on the reducing power of various organs was studied. Water and lipid soluble extracts were prepared from the brain, heart, lung, kidney, intestine, skin, and liver of control and traumatized rats (1 and 24 h after injury) and total LMWA was determined. Ascorbic acid, uric acid, alpha-tocopherol, carotene and ubiquinol-10 were also identified by HPLC. The dynamic changes in LMWA levels indicate that the whole body responds to CHI. For example, transient reduction in LMWA (p<0.01) in the heart, kidney, lung and liver at 1 h suggests their consumption, probably due to interaction with locally produced ROS. However, in some tissues (e.g., skin) there was an increase (p<0.01), arguing for recruitment of higher than normal levels of LMWA to neutralize the ROS. alpha-Tocopherol levels in the brain, liver, lung, skin, and kidney were significantly reduced (p<0.01) even up to 24 h. We conclude that although the injury was delivered over the left cerebral hemisphere, the whole body appeared to be under oxidative stress, within 24 h after brain injury.

Differences in the reducing power along the rat GI tract: lower antioxidant capacity of the colon

The ability of the gastrointestinal (GI) tract, as well as other tissues, to cope with reactive oxygen species (ROS) efflux in pathological events is determined partly by epithelial antioxidant levels. These levels are comprised of tissue antioxidant enzymes and low molecular weight antioxidants (LMWA). While glutathione levels and the activity of enzymatic antioxidants along the GI tract have been studied, the contribution of the overall LMWA to the total antioxidant capacity has not yet been determined. In this study the overall antioxidant activity in the mucosa/submucosa and muscularis/serosa of various sections along the small intestine and colon of the rat was evaluated by determining the reducing power, which reflects the total antioxidant activity derived from LMWA, using cyclic voltammetry. The activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase was also measured. The reducing power (total antioxidant activity) was higher in the mucosa/submucosa of the small intestine as compared to the mucosa/submucosa of the colon. Similarly, catalase and SOD activity in the mucosa/submucosa of the small intestine was significantly higher than in the mucosa/submucosa of the colon. Differences were also observed in the reducing power and SOD activity in the muscularis/serosa of the rat small intestine as compared to the colon. The low antioxidant capacity in the colon may facilitate reactive oxygen species (ROS)-mediated injury and lead to inflammatory diseases such as ulcerative colitis, specifically in the colon.

Noninvasive in vivo evaluation of skin antioxidant activity and oxidation status

The method described here allows noninvasive quantification of reducing LMWA or the lipid hydroperoxide present on the surface of the skin. Quantification of reducing antioxidants can be achieved because they are secreted from the skin surface into a well containing an extraction solution. Analysis of the reducing equivalents released indicates the presence of uric acid and ascorbic acid. Other LMWA released from the skin are as yet unidentified. The secretion of the LMWA reaches a plateau following 20-30 min of incubation. Therefore, a 30-min incubation period was chosen as the optimal time for the extraction solution to be present in the well and in contact with the skin. This extraction procedure can be repeated after 24 hr. This period of time is needed for regeneration of the LMWA to their initial levels. Direct measurement allows continuous determination of the release of LMWA and their interaction with the iron chelate. The reaction is completed after 25-35 min, at which time the final potential can be recorded. When organic peroxides on the surface of the skin are determined, it is important that the glassy carbon electrode be in close contact with the skin, since the reaction occurs on the surface of the electrode and the bound peroxide on the outer layer of the skin. Furthermore, close contact is needed to avoid interference of reducing equivalents secreted from the skin into the well.

Effect of a diet supplemented with thioproline on murine macrophage function in a model of premature ageing

A previous study has shown that diet supplementation with thioproline (thiazolidine-4-carboxylic acid, TCA), an intracellular sulfhydril antioxidant and free radical scavenger, stimulates lymphocyte functions in old mice. In the present work, the effect of thioproline ingestion on the phagocytic functions of peritoneal macrophages, namely adherence, chemotaxis, phagocytosis and superoxide anion production was studied in adult female OF1-Swiss mice, that were fed thioproline (0.1% w/w) for five weeks, starting this ingestion at the age of 22 +/- 2 weeks. Mice were divided into a fast and a slow group based on their exploratory activity, which was assessed by their performance in a T-shaped maze. Slow mice showed a worse phagocytic activity with respect to fast animals. After thioproline treatment, a stimulation of all the functions studied as well as a neutralization of the superoxide radical were observed. The effect of this antioxidant was stronger in the slow than in the fast group. Thus, a diet supplemented with thioproline may enhance the immune functions, especially when they are depressed.

Enhancement of leukocyte functions in aged mice supplemented with the antioxidant thioproline

Previous research has shown that supplementation of the diet with thioproline (thiazolidine-4-carboxylic acid), an intracellular sulfhydryl antioxidant and free radical scavenger, increases mouse life span and stimulates the immune system. In the present study aged Swiss mice (20 month old) fed thioproline (0.07%,w/w) for 5 weeks were used. Twelve month and 20 month old mice fed standard diet were used as controls. The lymphoproliferative response to the mitogen Concanavalin A (Con A) and the mobility of lymphocytes, both spontaneous and directed to a chemoattractant gradient (chemotaxis), as well as antibody-dependent cellular cytotoxicity (ADCC) and natural killer (NK) activity of leukocytes, were measured in cells from spleen and thymus. All of the above functions showed a significant decrease in aged (20 months) in comparison to adult mice (12 months). In aged animals, the ingestion of thioproline stimulated significantly the functions studied. Moreover, the age-related stress, revealed by the high corticosterone levels, was significantly decreased in animals fed this antioxidant. These data suggest that thioproline enhances immune response in the aged.

Oxidative stress in closed-head injury: brain antioxidant capacity as an indicator of functional outcome

It has been suggested that reactive oxygen species (ROS) play a role in the pathophysiology of brain damage. A number of therapeutic approaches, based on scavenging these radicals, have been attempted both in experimental models and in the clinical setting. In an experimental rat and mouse model of closed-head injury (CHI), we have studied the total tissue nonenzymatic antioxidant capacity to combat ROS. A major mechanism for neutralizing ROS uses endogenous low-molecular weight antioxidants (LMWA). This review deals with the source and nature of ROS in the brain, along with the endogenous defense mechanisms that fight ROS. Special emphasis is placed on LMWA such as ascorbate, urate, tocopherol, lipoic acid, and histidine-related compounds. A novel electrochemical method, using cyclic voltammetry for the determination of total tissue LMWA, is described. The temporal changes in brain LMWA after CHI, as part of the response of the tissue to high ROS levels, and the correlation between the ability of the brain to elevate LMWA and clinical outcome are addressed. We relate to the beneficial effects observed in heat-acclimated rats and the detrimental effects of injury found in apolipoprotein E-deficient mice. Finally, we summarize the effects of cerebroprotective pharmacological agents including the iron chelator desferal, superoxide dismutase, a stable radical from the nitroxide family, and HU-211, a nonpsychotoropic cannabinoid with antioxidant properties. We conclude that ROS play a key role in the pathophysiology of brain injury, and that their neutralization by endogenous or exogenous antioxidants has a protective effect. It is suggested, therefore, that the brain responds to ROS by increasing LMWA, and that the degree of this response is correlated with clinical recovery. The greater the response, the more favorable the outcome.