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Diverse functions of antioxidants
Abstract
All biological organisms have developed a defense system against oxidative stress, which is comprised of many kinds of antioxidants. Antioxidants are classified by function into four categories; preventive antioxidants; radical scavenging antioxidants; repair and de novo antioxidants; and adaptation. Radical scavenging antioxidants have the greatest advantage. Although the activities of radical scavenging antioxidant are determined by several factors, their chemical structure is of key importance. Furthermore, radical scavenging antioxidants have been explored to have a novel function by which they regulate gene expression of cell.
... Substances with functions concerning the membrane (vitamin A and E, βcarotene), circulation (vitamin C, amino acids and polyphenols), cytosol (co-enzyme Q10) are classified as antioxidants. In order to counteract intracellular damage by free radicals, cells have developed a so-called intracellular antioxidant system [26,27]. This process transforms free electrons into a nonreactive form by proteins (enzymes). ...
... Consequently, ROS activate matrix metalloproteases, thereby initiating intracellular signaling cascades to warn the nucleus of the presence of external stimulation. These changes in transcription and protein expression are observed after RF exposure [27]. Excessive elevation in ROS levels is an important cause of oxidative damage in lipids and proteins and nucleic acids. ...
... To a certain degree, antioxidants can neutralize the free radicals through homeostatic activity of the cells. If more ROS is generated than neutralized, then this system can shift and certain biomolecules become oxidized and/or altered [27]. In a pilot study [45] a special mouse model was used to show that long (ca. ...
Electromagnetic fields (EMF) have various chemical effects, including causing deterioration in large molecules in cells and imbalance in ionic equilibrium. Despite being essential for life, oxygen molecules can lead to the generation of hazardous by-products, known as reactive oxygen species (ROS), during biological reactions. These reactive oxygen species can damage cellular components such as proteins, lipids and DNA. Free radicals are unstable atoms or molecules with free outer electrons. This makes them highly reactive because free electrons always strive to form a stable bond. This stabilization involves gaining an electron from another molecule, triggering a chain reaction. Such reactions are omnipresent in the human body, but under certain circumstances can damage biomolecules. Whether nanoparticles are intracellular taken up leading to the activation of free radical production is currently being discussed. Ongoing studies are investigating whether the amount of free radicals formed on the surface of nanoparticles is sufficient to induce cellular effects. This dossier provides an overview about what free radicals are, how they originate, why organisms need them, how they are neutralized, and what we know about the connection between nanoparticles and free radical production. Several studies have reported that exposure to EMF results in oxidative stress in many tissues of the body. Exposure to EMF is known to increase free radical concentrations and traceability and can affect the radical couple recombination. The purpose of this review was to highlight the impact of oxidative stress on antioxidant systems.
... activity and ROS generation [77][78][79][80][81][82][83][84][85][86]. ...
... Regarding livestock, because of the production of oxygen radicals, an animal's high metabolic rate makes them more vulnerable to oxidative stress. As explained for sow reproduction, reproductive systems may also be affected by oxidative stress, and gestation may be considered an oxidative stress state because of increased placental mitochondrial activity and ROS generation [77][78][79][80][81][82][83][84][85][86]. ...
The perceived level of risk associated with a food product can influence purchase and consumption decisions. Thus, current trends in food safety address an issue of general interest—the identification of healthy and economical alternatives to synthetic antioxidants that may have harmful effects on human health. Still, the processors’ target is to increase the shelf life of food products using preserving substances. Natural antioxidants can be extracted and used in the food industry from different plants, such as blueberry, broccoli, chokeberry, cinnamon, ginger, olives, oregano, etc. The identification of the main natural antioxidant types that have been used in the food industry is very important in order to provide a comprehensive analysis of the researched topic. In this regard, the aim of this paper was to illustrate the positive aspects of using natural antioxidants with preservative roles in meat products, while, at the same time, highlighting the potential risks induced by these compounds. All of those aspects are correlated with the impact of sensorial attributes and the improvement of the nutritional value of meat products.
... The recorded analytical signal is proportional to the residual concentration of DPPH•, after its reaction with the antioxidant. Other redox couples used in biamperometric antioxidant capacity assay are ABTS +· /ABTS, Fe 3+ /Fe 2+ , Fe(CN) 6 3− /Fe(CN) 6 4− , Ce 4+ /Ce 3+ , VO 3 − /VO 2+ , and I 2 /I − [56,66,67]. The assay of total antioxidant capacity has been applied to the analysis of alcoholic beverages [56] and juices [68]. ...
... The recorded analytical signal is proportional to the residual concentration of DPPH•, after its reaction with the antioxidant. Other redox couples used in biamperometric antioxidant capacity assay are ABTS +· /ABTS, Fe 3+ /Fe 2+ , Fe(CN) 6 3− /Fe(CN) 6 4− , Ce 4+ /Ce 3+ , VO 3 − /VO 2+ , and I 2 /I − [56,66,67]. The assay of total antioxidant capacity has been applied to the analysis of alcoholic beverages [56] and juices [68]. ...
Antioxidants are compounds that prevent or delay the oxidation process, acting at a much smaller concentration, in comparison to that of the preserved substrate. Primary antioxidants act as scavenging or chain breaking antioxidants, delaying initiation or interrupting propagation step. Secondary antioxidants quench singlet oxygen, decompose peroxides in non-radical species, chelate prooxidative metal ions, inhibit oxidative enzymes. Based on antioxidants’ reactivity, four lines of defense have been described: Preventative antioxidants, radical scavengers, repair antioxidants, and antioxidants relying on adaptation mechanisms. Carbon-based electrodes are largely employed in electroanalysis given their special features, that encompass large surface area, high electroconductivity, chemical stability, nanostructuring possibilities, facility of manufacturing at low cost, and easiness of surface modification. Largely employed methods encompass voltammetry, amperometry, biamperometry and potentiometry. Determination of key endogenous and exogenous individual antioxidants, as well as of antioxidant activity and its main contributors relied on unmodified or modified carbon electrodes, whose analytical parameters are detailed. Recent advances based on modifications with carbon-nanotubes or the use of hybrid nanocomposite materials are described. Large effective surface area, increased mass transport, electrocatalytical effects, improved sensitivity, and low detection limits in the nanomolar range were reported, with applications validated in complex media such as foodstuffs and biological samples.
... [25,26] In this context, antioxidants compounds are able to delay or hinder oxidative damage on lipid peroxidation, sulfoxidation, nitration, protein carbonylation and DNA impairment induced by free radicals' excess. [27] Primarily, antioxidants act by scavenging radical species and converting them into more stable and harmless nonradical species, [28] and secondarily, by quenching singlet oxygen and decomposing peroxides to form non-radical species. Antioxidants also inhibit oxidative enzymes such as lipoxygenase, absorb UV radiation and can chelate with pro-oxidative metal ions. ...
Phenothiazines (PTZs) are an emerging group of molecules showing effectiveness toward redox signaling and reduction of oxidative injury to cells, via the activation on Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2 (Nrf2). Although several electrophilic and indirect Nrf2 activators have been reported, the risk of “off-target” effect due to the complexity of their molecular mechanisms of action, has aroused research interest toward non-electrophilic and direct modulators of Nrf2 pathway, such as PTZs. This review represents the first overview on the roles of PTZs as non-electrophilic Nrf2 activator and free radical scavengers, as well as on their potential therapeutic effects in oxidative stress-mediated diseases. Here, we provide a collective and comprehensive information on the PTZs ability to scavenge free radicals and activate the Nrf2 signaling pathway, with the aim to broaden the knowledge of their therapeutic potentials and to stimulate innovative research ideas.
... Ascorbic acid works synergistically with primary antioxidants like alpha-tocopherol. But L-ascorbic acid is poorly miscible with alpha-tocopherol or oily goods; hence it is preferable to employ ascorbyl fatty acid derivatives instead of vitamin C [86]. There is only one primary alcohol in ascorbic acid that can react with an acyl donor to produce the 6-O-ascorbyl ester. ...
Background
Lipases are carboxylic ester hydrolase enzymes, constituting the class of serine hydrolases, requiring no cofactor for their action.
Introduction
They have various substrates and produce glycerol and free fatty acids through the hydrolysis of fats and oils. Owing to their wide applications and the simplicity with which they can be mass-produced, these are a significant group of biotechnologically important enzymes. In addition, lipases have the special characteristic of operating at a lipid/water interface.
Result
Present review focuses on the medical and therapeutic use of lipases. These enzymes and their inhibitors have applications with remarkable success for managing or even treating diseases such as cancer, obesity, atherosclerosis, and Alzheimer’s. Lipases have also been used to produce healthier fatty acids and low-fat cheese.
Conclusion
The characteristic physicochemical and catalytic properties of enzymes make them ideal for biosensors and digestive aids in individuals with exocrine pancreatic inefficiency. Newer avenues open as deeper and more relevant studies are being conducted on newer lipases.
... Eventually, SOD was further inactivated. In addition to CAT, GSH can also prevent ROS production by neutralizing H 2 O 2 [33]. Enhanced GSH activity would help clear accumulated H 2 O 2 during the response to stress [34]. ...
The effects of various levels of alkalinity stress (0, 18.25, 35.41, 52.53 and 69.74 mmol/L) in Chinese mitten crab (Eriocheir sinensis) were investigated by means of measuring hepatopancreas antioxidant system and serum nonspecific immune system-related indices at 0, 12, 24, 48 and 96 h, hepatopancreas tissue structure at 96 h. The activities of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and aspartate aminotransferase (AST) in each concentration group generally showed a trend of a first increasing and then decreasing during the 96-h stress process (p < 0.05), while no significant changes were observed in the blank group during this period (p > 0.05). The activities of CAT, GSH and AST in all treatment reached peak values at 24–48 h. At 96 h of alkalinity stress, the activities of GSH, alanine aminotransferase (ALT), acid phosphatise (ACP) and alkaline phosphatise (AKP) in the 18.25 mmol/L group were not significantly different with the control group (p > 0.05). The activities of SOD and CAT in the 52.53 and 69.74 mmol/L treatment were significantly lower than those in the control group (p < 0.05), and the level of total antioxidant capacity(T-AOC), ALT, ACP and AKP in the 69.74 mmol/L group were significantly higher than those in the other groups (p < 0.05). Hepatopancreatic histological observation showed that the hepatopancreas of E. sinensis in the control group was normal. With increasing alkalinity, the basal membrane of the hepatopancreas fell off or even ruptured. Additionally, the number of hepatopancreas vacuoles increased, the volume of B cells and their internal transport vesicles increased, epithelial cells disintegrated, and the nucleus gradually shrank. E. sinensis can activate antioxidant and nonspecific immune systems to adapt to alkalinity stress. However, oxidative stress, immune system damage and hepatopancreas structure damage were caused when the stress exceeded the adaptive capacity of the body.
... 11 Human body has developed several endogenous antioxidants like superoxide dismutase, catalase, glutathione peroxidase and smaller molecules like vitamin C, vitamin E, reduced glutathione that scavenge the free radicals and inhibits the neoplastic process. 12 Any changes in one of these systems may break this equilibrium and cause cellular damages and ultimately malignant transformation. ...
... 11 Human body has developed several endogenous antioxidants like superoxide dismutase, catalase, glutathione peroxidase and smaller molecules like vitamin C, vitamin E, reduced glutathione that scavenge the free radicals and inhibits the neoplastic process. 12 Any changes in one of these systems may break this equilibrium and cause cellular damages and ultimately malignant transformation. ...
Oral cavity and the oropharynx are the two most common sites of cancer in the head and neck region. The exposure of
mucosal surface of the oral cavity and entire oropharynx to alcohol and tobacco-related carcinogens increases the risk for
developing premalignant or malignant lesions. The purpose of this study is to assess the serum levels of total antioxidant
capacity, vitamin C and malondialdehyde in confirmed cases of oral and oropharyngeal squamous cell carcinoma and
their correlation in healthy subjects.
... As for antioxidants, they are substances that prevent or slow down the generation of free radicals and oxidative processes in the body. Therefore, they form a line of defense against free radical activity and reactions [3]. Antioxidants are a substances that work to prevent or slow down the generation of free radicals and oxidative processes in the body. ...
Abstract. This study amid to evaluate the role of plant’s root (Astragalus spinosus), in biochemical parameters and histological sections effect in reduce the oxidative stress induced by hydrogen peroxide in rabbits Oryctalagus cuniculus, 7-9 months age and (1300-1500 g) of weight. Animals were distributed to three groups, every group were included five rabbits; group (1) control received water and diet. Group (2): animals treated with H2O2 (0.05) and drinking water. Group (3): animals treated with H2O2 and alcoholic extract of the plant root (5mg /kg body weight) for period one month. Study showed high significant increasing in Creatinine and ALP, LDH concentrations of animals treated with H2O2 alone (1.74±0.40) (9.900±1.058), (260.40±26.66) respectively, in compared with control (0.838±0.08)
(8.420±1.132), (154.0±49.79) respectively while the concentration of Creatinine, ALP and LDH had been decreased with high significant (P≤ 0.05) in group treated with H2O2 and extract of the plant roots (0.79±0.09), (9.220±0.801) and (166.2±36.08) respectively in compared with H2O2 group. And the result of histological sections of liver, kidneys and heart, which showed an improvement of cells in group treated with the extract of the plant which had
been induced by oxidative stress.
... Antioxidant molecules are considered as an option to treat oxidative damage and disorders caused by metals. 18 Polyphenolic compounds exhibit antioxidative and metal-chelating properties due to the presence of aromatic hydroxyl (OH) groups, the number of these groups in a compound, their location relative to each other, and the oxidative state of the Cring. 19 Some polyphenols, including catechins and catechin gallate, have been reported to possess high reactivity to Cu ions. ...
BACKGROUND
In this work, we investigated the antioxidant and copper chelating abilities of theaflavin, a polyphenol responsible for astringency, color, and sensation in black tea. Using voltammetric techniques, the analyses were conducted with disposable electrochemical printed carbon chips in conjunction with a portable hand‐held potentiostat.
RESULTS
Voltammograms of theaflavin showed five separate oxidation peaks, corresponding to the oxidation of five individual functional groups. Electroanalytical data indicated that, after interaction with copper, theaflavin had higher antioxidant potential and was a better copper chelator than epigallocatechin gallate, a major polyphenol present in green tea and a well‐known antioxidant. This could be attributed to the extra fused ring and larger number of OH groups in theaflavin.
CONCLUSIONS
Our findings introduce another natural compound as a potential nutraceutical in oxidation‐ and copper‐modulated illnesses. This simple and fast approach would also be highly pertinent to the inspection of the health benefits of natural food products. To the best of our knowledge, this is the first report of the electrochemical analysis of Cu (II) chelation with theaflavin. © 2020 Society of Chemical Industry
... Antioxidant defense system (ADS) versus oxidative stress is formed of various lines and antioxidants are divided into three divisions based on their use [197] First: defensive antioxidants which defeat formation of free radicals. ...
... Antioxidant molecules contain mainly a polyphenolic structure and possess the ability to scavenge and react preferentially with ROS [48]. They can be found in a variety of commonly consumed products, which are mainly obtained from plant sources. ...
Non-alcoholic fatty liver disease (NAFLD) is characterized by excess lipids in hepatocytes, due to excessive fatty acid influx from adipose tissue, de novo hepatic lipogenesis, in addition to excessive dietary fat and carbohydrate intake. Chronic hepatic lipid overload induces mitochondrial oxidative stress and cellular damage leading the development of NAFLD into a more severe liver disease condition, non-alcoholic steato-hepatitis (NASH). In turn, this can progress to cirrhosis and hepatocellular carcinoma (HCC). Among others, copper is one of the main bio-metals required for the preponderance of the enzymes involved in physiological redox reactions, which primarily occurs during mitochondrial respiration. Thus, copper homeostasis could be considered a target point for counteracting the progression of NAFLD. Accordingly, many diseases are correlated to unbalanced copper levels and, actually, some clinical trials are examining the use of copper chelating agents. Currently, no pharmacological interventions are approved for NAFLD, but nutritional and lifestyle modifications are always recommended. Fittingly, antioxidant food agents recognized to improve NAFLD and its complications have been described in the literature to bind copper. Therefore, this review describes the role of nutrition in the development and progression of NAFLD with a particular focus on copper and to copper-binding antioxidant compounds against NAFLD.
... Vitamin C is often applied alone or in combination with synergists (e.g. vitamin E) for preservation of food, beverages, cosmetic, and pharmaceutical products [213]. However, it is immiscible with lipids, so its efficiency in products containing them is considerably diminished. ...
The esterification is well-established type of reaction in organic synthesis used for manufacturing various valuable esters used prevalently as ingredients of food, skincare products, pharmaceuticals and fuels. In recent decades biocatalytic synthetic routes based on using enzymes as catalysts have received a lot of attention in scientific researches and industry. Main advantages of enzymatic esterifications are high selectivity (regioselectivity and enantioselectivity), performing reaction at milder conditions (moderate temperature and atmospheric pressure) and the fact that enzymatically synthesized product gain label of natural product, which increases its market appeal. The purpose of this review is to point out the most important advances in lipase-catalyzed ester synthesis in non-conventional reaction media, with special focus on several most important types of ester. This part of review starts with outcomes in synthesis of aroma esters, usually obtained using monofunctional aliphatic alcohols and acids, which have been investigated for decades and industrial processes are already established. However, later sections are dedicated to enzymatic esterification of more complex molecules (carbohydrates, vitamin C, flavonoids) having more than one functional groups, which are subject of numerous studies in recent times because in these reactions regioselectivity of biocatalysts can be fully explored and processes are still subject of optimization, especially with respect to selection of reaction media and media engineering.
... LDL can incorporate endogenous and exogenous antioxidants in its supramolecular structure, decreasing its susceptibility to be oxidized. In fact, many endogenous and exogenous compounds have been reported to display beneficial effects against LDL oxidation (Noguchi et al. 2000, Chu and Liu 2005, Barcelos et al. 2011. However, the strategies with antioxidants supplementation had generated both "positive" and "no response" effects in decreasing atherogenesis (Rahman et al. 2014). ...
Oxidation of low-density lipoprotein (LDL) has been strongly suggested to play a significant role in the pathogenesis of atherosclerosis. Thus, reducing LDL oxidation is a potential approach to decrease the risk of the atherosclerosis. Organoselenium compounds have demonstrated promising atheroprotective properties in experimental models. Herein, we tested the in vitro atheroprotective capability of a modified organoselenium compound, Compound HBD, in protecting isolated LDL from oxidation as well as foam cells formation. Moreover, the glutathione peroxidase (GPx)-like activity of Compound HBD was analyzed in order to explore the mechanisms related to the above-mentioned protective effects. The Compound HBD in a concentration-dependent manner reduced the Cu2+-induced formation of conjugated dienes. The protein portion from LDL were also protected from Cu2+-induced oxidation. Furthermore, the Compound HBD efficiently decreased the foam cell formation in J774 macrophage cells exposed to oxidized LDL. We found that the atheroprotective effects of this compound can be, at least in part, related to its GPx-like activity. Our findings demonstrated an impressive effect of Compound HBD against LDL-induced toxicity, a further in vivo study to investigate in more detail the antioxidant and antiatherogenic effects of this compound could be considered.
... The most important defenses are oxidative enzymes such as catalase and superoxide dismutase and other low-molecular-weight molecules such as vitamin C or E and glutathione that scavenge free radicals. Other important molecules involved in metal chelation are ferritin and transferritin (Noguchi, Watanabe, & Shi, 2000) and recently attention has been given to the antioxidant peptides. ...
Amaranth seeds have a high content of bioactive compounds with a remarkable nutritional and nutraceutical positive potential for human health. Their composition includes key proteins, some interesting essential amino acids, lipids, carbohydrates, dietary fiber and important phytochemicals. Since the last decades amaranth has been considered the most promising plant due to its agronomic performance, protein quality and essential amino acids of their seeds superior to other important cereals. Globulins are the main protein fraction containing valuable amounts of essential amino acids. When amaranth proteins are subjected to enzymatic proteolysis by food processing, bioactive peptides are released and their absorption may bring benefits to health. The functional properties of the bioactive peptides including their antihypertensive and antioxidant properties may prevent the onset of cardiovascular diseases and favor other outstanding health benefits. The use of prediction of sequence peptides and other molecular tools are giving place to genetic transformation and modifications which may conduct to the improvement of the nutraceutical potential of these proteins.
... 11 Human body has developed several endogenous antioxidants like superoxide dismutase, catalase, glutathione peroxidase and smaller molecules like vitamin C, vitamin E, reduced glutathione that scavenge the free radicals and inhibits the neoplastic process. 12 Any changes in one of these systems may break this equilibrium and cause cellular damages and ultimately malignant transformation. ...
Oral cavity and the oropharynx are the two most common sites of cancer in the head and neck region. The exposure of
mucosal surface of the oral cavity and entire oropharynx to alcohol and tobacco-related carcinogens increases the risk for
developing premalignant or malignant lesions. The purpose of this study is to assess the serum levels of total antioxidant
capacity, vitamin C and malondialdehyde in confirmed cases of oral and oropharyngeal squamous cell carcinoma and
their correlation in healthy subjects.
... Antioxidants are classified into three categories [56][57][58] as follows: ...
In this modern world, due to the rapid advancement of civilization, industrialization, and overpopulation, scientific knowledge on antioxidants is important since most of the dis‐ eases are mediated through reactive oxygen species (ROS). An antioxidant is a molecule that inhibits the oxidation of another molecule. Antioxidants may work through single or combined mechanisms, and based on their activity, they have been categorized into pri‐ mary, secondary, and tertiary antioxidants. Enzymatic and non-enzymatic antioxidants are the two widely accepted categories of antioxidants. In addition to natural antioxi‐ dants, synthetic antioxidants have been extensively used in medicinal and food indus‐ tries. In brief, antioxidants play a significant role in ameliorating toxicity through free radical scavenging reactions and therefore have potential therapeutic value.
... Diethyl nitrosamine (Dena) is well known to induce liver cancer due the release of reactive oxygen species and inducing oxidative stress. it metabolized to reactive electrophilic reactants that alter the structure of Dna and forms alkyl Dna adducts 5 . ...
Hepatocellular carcinoma (HCC) is the fifth and third most common cause of cancer-related deaths. Erythrosine, a commonly used coloring agent in tablet preparation was studied for its role when supplemented with sub necrotic dose of DENA (n-diethyl nitrosamine) to induced HCC in Wistar rats. Single dose of chemical carcinogen DENA with intraperitoneal injection (20 mg/kg) administered before Erythrosine at a dose 0.014 mg/kg by p.o, DENA treated rats and alone. Exposure of DENA and Erythrosine alters the levels of Serum glutamate oxaloacetate transaminase (SGoT), Serum glutamate pyrophosphate transaminase (SGPT), Alkaline phosphate (ALP), Total Bilirubin (TBR), Blood uric acid, urea, lipid profile and Serum alpha-feto protein (AFP) in Wistar rats, with further alteration in intracellular antioxidant enzyme profile Lipid Per oxidation (LPo), Glutathione Peroxidase (GPx), Melanoaldehyde (MDA), Glutathione Reductase (GR), Catalase (CAT), Glutathione (GSH), Glutathione-S-Transferase (GST), Superoxide Dismutase (SoD) along with Vit. C and Vit. E conc. Moreover Histopathological examinations of the liver tissue showed marked effect of DENA and Erythrosine exposure on liver structure. The results concluded that Erythrosine used as coloring agent for tablet coating as well as food colorant in India, was found to be an inducer as liver proliferating agent and promoter of HCC. © 2015, The Korean Society of Toxicogenomics and Toxicoproteomics and Springer Science+Business Media Dordrecht.
... Besides, the human body has diverse defense antioxidant mechanisms that can act at different levels of the oxidation process. The most important defense mechanisms are antioxidant enzymes, free radical scavengers, and metal chelators (Noguchi et al., 2000). When free radicals are generated in excess or when cellular defenses are deficient, biomolecules are damaged by a process named oxidative stress (Mendis et al., 2007). ...
Seed storage proteins have been nutritional and functionally valuable in the food industry and for human consumption. The Osborne's classical technique has been used to extract and classify seed storage proteins; additionally, in the last decades molecular properties have been also used for their characterization. Amaranth proteins, most of them being globulins (salt soluble proteins), have good essential amino acid levels. The nutritional, nutraceutical and technological properties shown by amaranth make it highly attractive to be incorporated into food formulations and to complement or replace some conventional cereal grains. The functional properties of its proteins provide good technological characteristics to food matrices. Several studies have shown that globulins are involved in some immunological processes suggesting that the immune-stimulating effects may lead to B lymphocyte activation and subsequent T cell proliferation in vitro. Other bioactive properties have been found in peptides from globulins mainly as outstanding antihypertensive agents. The previous characteristics, plus some others, are showing that the strong potential of amaranth and especially of its globulins should lead both of them to wider food and nutraceutical uses.
... Besides, the human body has diverse defense antioxidant mechanisms that can act at different levels of the oxidation process. The most important defense mechanisms are antioxidant enzymes, free radical scavengers, and metal chelators (Noguchi et al., 2000). When free radicals are generated in excess or when cellular defenses are deficient, biomolecules are damaged by a process named oxidative stress (Mendis et al., 2007). ...
... 16,17 ROS-generating mechanism of Pb is mediated by delta-aminolevulinic acid dehydratase (δ-ALAD) inhibition, which provokes the accumulation of delta-aminolevulinic acid (δ-ALA) 16,18 Defense against xenobiotic toxicity, which is composed of many types of antioxidants, is well characterized in mammals. 19,20 We report here our study of the role of oxidative damage (and its modulation) in events evoked by the As-Cd-Pb metal mixture, in which we analyze the involvement of two preventive antioxidant compounds (catalase and glutathione) and their inhibitors in the modulation of the transformation process. ...
Introduction:
Metals are ubiquitous soil, air, and water pollutants. A mixture of arsenic cadmium and lead, in particular, has commonly been found in the vicinity of smelter areas. The mixture of As-Cd-Pb has been shown to be carcinogenic, and transforming potential and oxidative stress have been proposed as principal mechanisms involved in this process. The aim of this work was to explore the role of the antioxidant barrier in the establishment of cell transformation upon chronic exposure to a metal mixture containing 2 μM NaAsO(2), 2 μM. CdCl(2), and 5 μM Pb(C(2)H(3)O(2))(2)∙3H(2)O in WRL-68 cells-a non-transformed human hepatic cell line.
Material and methods:
In this study, we used a WRL-68 cell model of human embryonic hepatic origin treated with antioxidant inhibitors (L-Buthionine-sulfoxamine and aminotriazole) to test the role of the antioxidant barrier in the establishment of cell transformation upon chronic exposure to a metal mixture of As-Cd-Pb (2 μM NaAsO(2), 2 μM CdCl(2) and 5 μM Pb(C(2)H(3)O(2))(2)∙3H(2)O). We evaluated oxidative damage markers, including reactive oxygen species, lipid peroxidation, and genotoxicity, as well as antioxidant response markers, including glutathione concentration, catalase activity, and superoxide dismutase activity, which promote morphological transformation, which can be quantified by foci formation.
Results:
As expected, we found an increase in the intracellular concentration of the metals after treatment with the metal mixture. In addition, treatment with the metal mixture in addition to inhibitors resulted in a large increase in the intracellular concentration of cadmium and lead. Our results describe the generation of reactive oxygen species, cytotoxicity, genotoxicity, and oxidative damage to macromolecules that occurred exclusively in cells that were morphologically transformed upon exposure to a metal mixture and antioxidant barrier inhibition.
Conclusion:
Our results show the importance of the antioxidant barrier role in the protection of cellular integrity and the transformation potential of this metal mixture via free radicals.
... N-Nitrosodiethylamine (DENA) is the most important environmental carcinogen among the nitrosamines (Thirunavukkarasu and Sakthisekaran, 2001). DENA has been suggested to cause oxidative stress and cellular injury due to involvement of free radicals (Noguchi et al., 2000). Lipid peroxidation and associated membrane damage are key features of DENA-induced carcinogenesis (Anis et al., 2001). ...
The present study was conducted to investigate the chemopreventive effects of hydro-ethanolic extract of
Euphorbia neriifolia (EN) on N-nitrosodiethylamine (DENA) induced renal cancer in male Swiss albino mice.
Animals were pretreated with EN extract (150 and 400 mg/kg body weight; p.o) and butylated hydroxyanisole
(BHA) as a standard (0.5% and 1% BHA p.o) both for two week prior to the administration of single dose of
DENA (50 mg/kg body weight; p.o). Various in vivo antioxidant biochemical parameters like lipid peroxidation
(LPO), superoxide dismutase (SOD), and catalase (CAT) were evaluated to determine the reno-protective and
antioxidant activity of EN. DENA increased oxidative stress through increase in LPO and decrease in antioxidant
enzymes (SOD, and CAT). The EN extract significantly restored the antioxidant enzyme level in the kidney
and exhibited significant dose dependant protective effect against DENA induced nephrotoxicity, which can be
mainly attributed to the antioxidant property of the extract. This study rationalized the ethno-medicinal use of
EN for protection against renal cancer.
... glutathione, vitamin C, vitamin E), and metal chelators (e.g. transferrin, ferritin) (Noguchi, Watanabe & Shi, 2000). When free radicals are generated in excess or when cellular defenses are deficient, biomolecules are damaged by a process named oxidative stress (Mendis, Kim, Rajapakse & Kim, 2007). ...
The antioxidant activity of peptides present in the phosphate buffer-soluble fraction of: – Amaranthus mantegazzianus protein isolates (Is), – protein fractions (Albs, Globs, GlobPs and Gluts), alcalase hydrolysates of isolates (hydrolysis degree –HD-: 2.4% (IHls) and 30% (IHhs) and protein fractions (AlbHs, GlobHs, GlobPHs, and GlutHs) was investigated. Fractions separated by molecular exclusion chromatography were also analyzed. ABTS+. scavenging method showed the presence of antioxidant peptides in Is, Albs, Globs, and Gluts, being the last the one with the highest activity. No activity was detected in the GlobPs. After hydrolysis, the scavenging activity of all samples increased, especially at high HD. The GlobPs fraction presented the highest scavenging capacity after hydrolysis. Naturally-occurring peptides and polypeptides presented also the capacity to inhibit the linoleic acid oxidation, which was partially lost after hydrolysis. FPLC fractionation evidenced the appearance of <0.5 kDa active peptides due to the hydrolysis process. Results suggest the presence in the Is and IHhs of several peptides and polypeptides which can act as antioxidants by different mechanisms.
... Antioxidants can be classified into four categories based on function. (1) Preventive antioxidants which suppress formation of ROS, (2) radical scavenging antioxidants which suppress chain initiation and/or break chain propagation reactions, (3) the repair and de novo antioxidants such as proteolytic enzymes and the repair enzymes of DNA, and (4) antioxidants which allow for adaptation that occurs when Enzymatic antioxidants located in mitochondria and cytosol Glutathione peroxidase (GSH) Removal of H 2 O 2 , hydroperoxides Superoxide dismutase (SOD) Catalytic removal of O 2 Catalase (CAT) Catalytic reduction of H 2 O 2 to H 2 O Nonenzymatic antioxidants located in cell membrane, exogenous dietary source Vitamin E (α tocopherol) Chain-breaking antioxidant β-carotene Scavenger of ROS, singlet O 2 quencher Co-enzyme Q Regenerates vitamin E Compounds that reduce the availability of transition metals, Fenton reactions Transferrin Sequesters iron and copper ions Lactoferrin Sequesters iron at lower pH Albumin Sequesters heme and copper Ceruloplasmin (ferroxidase) Scavenges superoxide radical, binds copper ions Scavengers, products of metabolism, exogenous dietary source Bilirubin Scavenges peroxyl radical Uric acid Scavenges hydroxyl radical Vitamin C (ascorbic acid) Scavenges hydroxyl radical, recycles vitamin E Thiol group donors Reduced glutathione (GSSH) Binds free radicals, SH group oxidized to disulfide group (GSSG) α-lipoic acid Recycles vitamin C, glutathione substitute the signal for the production and reactions of ROS induces oxidant formation and transport [10, 61]. Superoxide dismutase converts O 2 @BULLET− to H 2 O 2 and has three isoforms widely distributed in mammalian organisms. ...
Oxygen (O(2)) is life essential but as a drug has a maximum positive biological benefit and accompanying toxicity effects. Oxygen is therapeutic for treatment of hypoxemia and hypoxia associated with many pathological processes. Pathophysiological processes are associated with increased levels of hyperoxia-induced reactive O(2) species (ROS) which may readily react with surrounding biological tissues, damaging lipids, proteins, and nucleic acids. Protective antioxidant defenses can become overwhelmed with ROS leading to oxidative stress. Activated alveolar capillary endothelium is characterized by increased adhesiveness causing accumulation of cell populations such as neutrophils, which are a source of ROS. Increased levels of ROS cause hyperpermeability, coagulopathy, and collagen deposition as well as other irreversible changes occurring within the alveolar space. In hyperoxia, multiple signaling pathways determine the pulmonary cellular response: apoptosis, necrosis, or repair. Understanding the effects of O(2) administration is important to prevent inadvertent alveolar damage caused by hyperoxia in patients requiring supplemental oxygenation.
... 3 This stress has been implicated in the pathogenesis of major diseases such as cancer, rheumatoid arthritis, post-ischemic injury, degenerative process of aging, myocardial infarction, cardio-vascular diseases. 4 The human body has evolved a large array of endogenous antioxidant defenses against oxidative stress, including antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and various peroxidases 5 and certain small molecules with antioxidant activity such as glutathione, 6 the hormone melatonin, 7 uric acid, 8 and ceruloplasmin. 9 These endogenous defenses do not completely protect against the sum of oxidative stresses challenging the body, and there is net oxidative damage, thus necessitating the need for exogenous natural antioxidants. ...
Protective role of thyme extract against N-nitrosodiethylamine (NDEA)-induced oxidative stress has been evaluated in albino rats. For this, one group of rats were fed diet supplemented with thyme extract (0.5%) and served as the test group, whereas animals of the other group fed on normal diet served as the control group. The rats were fed on respective diets for a period of 2 weeks after which stress was induced to half the animals of each group by i.p. administration of NDEA at 200 mg/kg body weight. Animals were killed 48 h post stress-induction period. Feed intake and body weight decreased significantly in both test and control groups, the effect being less in test group. Increase in osmotic fragility and in-vitro lipid peroxidation (LPO) on stress induction was of lower degree in the test group. NDEA toxicity was mainly reflected in liver as evidenced by increased activities of plasma aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase. The effect was of lower degree in test group as compared with that in the control group. Increase in urea levels observed following NDEA administration was also of lower degree in test groups. Blood glutathione (GSH) levels increased more so in test group compared with control group on stress induction. The activities of superoxide dismutase (SOD), peroxidase (Px), and catalase (CAT) activities decreased significantly on stress induction in erythrocytes. LPO increased in all the tissues through varying degree, and the increase was appreciably of lower degree in test group. The activity of SOD increased significantly in both test and control group on stress induction, whereas activities of Px and CAT decreased following NDEA treatment, and the effects were of lower degree in test group. Thus, supplementation of diet with thyme extract can improve antioxygenic potential and hence help to prevent oxidative stress.
As a requirement of aerobic metabolism, regulation of redox homeostasis is indispensable for the continuity of living homeostasis and life. Since the stability of the redox state is necessary for the maintenance of the biological functions of the cells, the balance between the pro-oxidants, especially ROS and the antioxidant capacity is kept in balance in the cells through antioxidant defense systems. The pleiotropic transcription factor, Nrf2, is the master regulator of the antioxidant defense system. Disruption of redox homeostasis leads to oxidative and reductive stress, bringing about multiple pathophysiological conditions. Oxidative stress characterized by high ROS levels causes oxidative damage to biomolecules and cell death, while reductive stress characterized by low ROS levels disrupt physiological cell functions. The fact that ROS, which were initially attributed as harmful products of aerobic metabolism, at the same time function as signal molecules at non-toxic levels and play a role in the adaptive response called mithormesis points out that ROS have a dose-dependent effect on cell fate determination.
See also Figure 1(Fig. 1).
Although many diseases in which reactive oxygen species (ROS) and free radicals are involved in their pathogenesis are known, and antioxidants that effectively capture ROS have been identified and developed, there are only a few diseases for which antioxidants have been used for treatment. Here, we discuss on the following four concepts regarding the development of applications for disease treatment by regulating ROS, free radicals, and lipid oxidation with the findings of our research and previous reports. Concept 1) Utilization of antioxidants for disease treatment. In particular, the importance of the timing of starting antioxidant will be discussed. Concept 2) Therapeutic strategies using ROS and free radicals. Methods of inducing ferroptosis, which has been advocated as an iron-dependent cell death, are mentioned. Concept 3) Treatment with drugs that inhibit the synthesis of lipid mediators. In addition to the reduction of inflammatory lipid mediators by inhibiting cyclooxygenase and leukotriene synthesis, we will introduce the possibility of disease treatment with lipoxygenase inhibitors. Concept 4) Disease treatment by inducing the production of useful lipid mediators for disease control. We describe the treatment of inflammatory diseases utilizing pro-resolving mediators and propose potential compounds that activate lipoxygenase to produce these beneficial mediators.
Fluctuations of dissolved oxygen (DO) frequently lead to a hypoxic condition in aquaculture, and hypoxia exerts tremendously adverse effects on fish. The present study mainly investigated the effects of chronic hypoxia on growth performance, antioxidant capacity and protein turnover of largemouth bass (Micropterus salmoides). The fish were exposed to normoxic (86%–95% DO saturation), mild hypoxic (51%–60% DO saturation) and severe hypoxic (17%–26% DO saturation) conditions for 6 weeks, respectively. Results showed that chronic hypoxia significantly reduced the weight gain rate, specific growth rate and feed intake of largemouth bass. The activities of SOD and CAT in serum, as well as SOD and GPX in muscle, were significantly increased in the severely hypoxic condition. The histological analysis showed that the mean diameter of myofiber was significantly decreased during severe hypoxia. Additionally, the levels of gene and protein revealed that chronic severe hypoxia inhibited protein synthesis by downregulating the HIF-1α/REDD1/mTOR signal pathway and promoted protein degradation by activating the pathways of ubiquitin-proteasome, autophagy-lysosome and calcium proteasome. Overall, this study indicated that chronic hypoxia decreased the growth performance of largemouth bass. Meanwhile, chronic severe hypoxia not only enhanced antioxidant capacity, but also contributed to orient in the balance of protein turnover towards catabolism thus causing muscle atrophy. We suggested that for better growth of fish, the dissolved oxygen concentration should be maintained above 60% DO saturation in aquaculture.
The present review paper focuses on the chemistry of oxidative stress mitigation by antioxidants. Oxidative stress is understood as a lack of balance between the pro-oxidant and the antioxidant species. Reactive oxygen species in limited amounts are necessary for cell homeostasis and redox signaling. Excessive reactive oxygenated/nitrogenated species production, which counteracts the organism's defense systems, is known as oxidative stress. Sustained attack of endogenous and exogenous ROS results in conformational and oxidative alterations in key biomolecules. Chronic oxidative stress is associated with oxidative modifications occurring in key biomolecules: lipid peroxidation, protein carbonylation, carbonyl (aldehyde/ketone) adduct formation, nitration, sulfoxidation, DNA impairment such strand breaks or nucleobase oxidation. Oxidative stress is tightly linked to the development of cancer, diabetes, neurodegeneration, cardiovascular diseases, rheumatoid arthritis, kidney disease, eye disease. The deleterious action of reactive oxygenated species and their role in the onset and progression of pathologies are discussed. The results of oxidative attack become themselves sources of oxidative stress, becoming part of a vicious cycle that amplifies oxidative impairment. The term antioxidant refers to a compound that is able to impede or retard oxidation, acting at a lower concentration compared to that of the protected substrate. Antioxidant intervention against the radicalic lipid peroxidation can involve different mechanisms. Chain breaking antioxidants are called primary antioxidants, acting by scavenging radical species, converting them into more stable radicals or non-radical species. Secondary antioxidants quench singlet oxygen, decompose peroxides, chelate prooxidative metal ions, inhibit oxidative enzymes. Moreover, four reactivity-based lines of defense have been identified: preventative antioxidants, radical scavengers, repair antioxidants, and those relying on adaptation mechanisms. The specific mechanism of a series of endogenous and exogenous antioxidants in particular aspects of oxidative stress, is detailed. The final section resumes critical conclusions regarding antioxidant supplementation.
Older people are increasing in number worldwide and they are affected by neurodegenerative disorders. Tauopathies are neurodegenerative disorders that involve diseases such as progressive supranuclear palsy (PSP), frontotemporal dementia linked to chromosome 17 (FTD-17), corticobasal degeneration, and Alzheimer's disease (AD) among others. Other neurodegenerative disorders such as Parkinson's disease is characterized for inclusion denominated as Lewis bodies conformed by hyperphosphorylated alpha-synuclein protein (α-syn). However, there are some neurodegenerative disorders that overlap each other such as dementia with Lewy bodies (DLB), Lewy body variant of AD and Parkinson's disease with dementia (PDD). Moreover, there is an increase in the number of patients of PD with dementia and patients with AD with Lewy body's inclusions in post mortem samples. Thus, we find pertinent to discuss both covalent and noncovalent inhibitors targeting alpha-synuclein and tau.
Carrot (Daucus carota L.) is an important vegetable source of bioactive compounds having significant health-promoting properties beyond basic nutrition. Higher intakes of carotenoids are associated with an enhancement of the immune system, and decreased risk of various cancers and degenerative diseases. Further, the presence of phenolic compounds is responsible for the aroma and bitterness of carrots, as well as strong antioxidant potential. Carrot processing generates wastes in the form of peels and pomaces, which can create serious nutritional, economic, and environmental problems. Carrot waste contains high amounts of residual bioactives, with currently little commercial values. These phytochemicals could be profitably utilized for the fortification and development of functional foods, pharmaceuticals, and medicines. This review describes carrot waste as a source of natural bioactive compounds, with health-promoting properties and potential applications in the food and pharmaceutical industries.
أجريت هذه الدراسة لمعرفة تأثير مسحوق جذور عرق السوس Licorice Roots في حالة مضادات الأكسدة وبعض المؤشرات الفسلجية في مصل دم طائر السمان. إذ وزع عشوائياً 100 طائراً من إناث السمان المحلية Coturnix coturnix بعمر 49 يوماً في أربع مجموعات (25 أنثى/ مجموعة) وبواقع 5 مكررات/ مجموعة، واستمرت المعاملة لغاية عمر 91 يوماً. وكانت مجموعات الدراسة كالآتي: المجموعة الأولى (مجموعة السيطرة) ربيت على عليقة قياسية خالية من عرق السوس، بينما ربيت المجموعة الثانية والثالثة والرابعة على عليقة قياسية مضافاً إليها 500 و1000 و1500 ملغم من مسحوق جذور عرق السوس/ كغم علف على التوالي. قدم العلف والماء بشكل حر ad libitum أمام الطيور طيلة مدة الدراسة. تبين من النتائج أن الإضافة العلفية لمسحوق جذور عرق السوس قد عززت من حالة مضادات الأكسدة، تمثلت بارتفاع معنوي لمستوى الكلوتاثيون (GSH)Glutathione وانخفاض معنوي لمستوى المالوندايالديهايد (MDA) Malondialdehyde في مصل دم طيور معاملات جذور عرق السوس مقارنة مع مجموعة السيطرة عند مستوى احتمال (أ ≤ 0.05)، كما أدت الإضافة إلى انخفاض معنوي (أ ≤ 0.05) في مستوى كل من الكولسترول والكليسيريدات الثلاثية في مصل دم طيور معاملات جذور عرق السوس مقارنة مع مجموعة السيطرة. ومن ناحية أخرى، لم يكن هنالك فروق معنوية (أ ≤ 0.05) بين المعاملات في مستوى كل من الكلوكوز والبروتين الكلي في مصل الدم ومقارنة مع مجموعة السيطرة. بشكل عام، بينت الدراسة أن لمسحوق جذور عرق السوس قدرة مضادة للأكسدة تمثلت في تحسين حالة مضادات الأكسدة وبعض المعايير الكيموحيوية في مصل دم إناث طائر السمان.
The use of traditional herbal remedies as alternative medicine plays an important role in Africa since it forms part of primary health care for treatment of various medical conditions, including wounds. Although physiological levels of free radicals are essential to the healing process, they are known to partly contribute to wound chronicity when in excess. Consequently, antioxidant therapy has been shown to facilitate healing of such wounds. Also, a growing body of evidence suggests that, at least, part of the therapeutic value of herbals may be explained by their antioxidant activity. This paper reviews African herbal remedies with antioxidant activity with the aim of indicating potential resources for wound treatment. Firstly, herbals with identified antioxidant compounds and, secondly, herbals with proven antioxidant activity, but where the compound(s) responsible for the activity has not yet been identified, are listed. In the latter case it has been attempted to ascribe the activity to a compound known to be present in the plant family and/or species, where related activity has previously been documented for another genus of the species. Also, the tests employed to assess antioxidant activity and the potential caveats thereof during assessment are briefly commented on.
Objective: To study the cellular and molecular mechanisms by which the antioxidants of Ginkgo biloba extract (EGb761) inhibit AFB1-induced toxic changes in human hepatocytes (HepG2 cells). Methods: HepG2 cells were subjected to various concentrations of AFB1 in culture medium. The inhibitory rate of cell growth was measured by MTT assay. The cell survival effects of EGb761 was determined by using MTT and FCM on the cells exposed to AFB1. Finally, the products of oxidative reaction such as the reactive oxygen species (ROS) and malondialdehyde (MDA) in the HepG2 cells were measured by dichlorodihydrofluorescein diacetate (DCFH-DA) and thibabituric acid (TBA) assays. Results: AFB1 exhibited significant cytotoxicity to HepG2 cells, IC50 was 15 μg/mL. At different time (24, 48 and 72 hours), EGb761 (219 μg/ mL) could effectively inhibite the decreases of the cells viability (28%, 47% and 47%) and the enhancement of intracellular ROS level and MDA formation induced by AFB1 (15 μg/mL), P < 0.01. Conclusion: HepG2 cells pre-treated with EGb761 are protected from the toxic effects of AFB1 at both the cellular and molecular levels which the possible underlying mechanism is its antioxidation.
Physical activity is recognized as an important component of healthy life style and recommended throughout life by scientists and clinicians. Exercise training is recommended for improving physiological and functional capacity in the elderly. Intracellular levels of reactive oxygen species may be crucial for determining whether the cells undergo differentiation, proliferation or apoptosis because it has been shown that at low concentration.H2O2 induces necrosis in fibroblasts, while at high concentrations it causes a transient cell growth arrest by inducing the expression of gadd 45,153 and adapts 15 genes. The human body is constantly under attack from free radicals. Free radicals are highly reactive molecules generated by the biochemical redox reaction that occur as part of normal cell metabolism and by exposure to environment factors. The main free radical oxygen species O·2-OH which occur in human body include; super oxide radical (O2), hydroxyl radial (OH), nitric oxide radical NO· ROO· (NO), peroxyl radical (ROO). Once formed free radicals attack cell structures within the body. Decomposition of peroxidised lipids yields a wide variety of end products including malondialdehyde. The imbalance between process forming oxygen free radicals and endogeneous defence system results in oxidative stress, it may play a major role in numerous diseases artherosclerosis, cancer, diabetes, respiratory diseases, liver damage, AIDS, central nervous system disorders, Parkinson disease, etc.
Through the research on the antioxidant activity and product yield of products by hydrolysis of oat protein with Alcalase, Trypsin and Pepsin respectively, it was determined that Alcalase was identified as the initial enzyme for preparing the antioxidative peptides. It was determined that the activity of oat protein products hydrolysised by Alcalase+ Trypsin and Alcalase+Pepsin respectively. Through the study on the velocity of the hydrolysis of oat bran protein with Alcalase, the result illustrated the decrease of velocity was mainly due to the consumption of substrate and the loss of enzyme activity. ©, 2014, Chinese Institute of Food Science and Technology. All right reserved.
The development of therapeutic compounds that can attenuate the toxicity exerted by the accumulation of metal ions has been an area of intensive research in neurodegenerative diseases. In this report, an electrochemical method was developed to determine the Cu(II)-chelating ability of polyphenols that were implicated in Alzheimer’s disease (AD). The results suggested the strength of flavonoids to chelate Cu(II) as epigallocatechin-3-gallate (EGCG)>resveratrol>clioquinol>baicalein∼scyllo-inositol. Furthermore, the number of hydroxyl groups was found to play a role to lower Cu(II) oxidation signal using differential pulse voltammetry.
Hyperphysiological burden of free radicals causes imbalance in homeostatic phenomena between oxidants and antioxidants in the body. This imbalance leads to oxidative stress that is being suggested as the root cause of aging and various human diseases like atherosclerosis, stroke, diabetes, cancer and neurodegenerative diseases such as Alzheimer's disease and Parkinsonism. Therefore, in modern Western medicine, the balance between antioxidation and oxidation is believed to be a critical concept for maintaining a healthy biological system. Researches in the recent past have accumulated enormous evidence advocating enrichment of body systems with antioxidants to correct vitiated homeostasis and prevent the onset as well as treat the disease caused/fostered due to free radicals and related oxidative stress. This article presents current understanding of the role of free radicals and oxidative stress in pathogenesis of various diseases and advancements made in developing antioxidant-based therapeutics and also discuss the opportunities to develop therapeutics from traditional medicinal practice.
We evaluated the capacity of simulated gastrointestinal digests or alcalase hydrolysates of protein isolates from amaranth to scavenge diverse physiologically relevant reactive species. The more active hydrolysate was obtained with the former method. Moreover, a prior alcalase treatment of the isolate followed by the same simulated gastrointestinal digestion did not improve the antioxidant capacity in any of the assays performed and even produced a negative effect under some conditions. Gastrointestinal digestion produced a strong increment in the scavenging capacity against peroxyl radicals (ORAC assay), hydroxyl radicals (ESR-OH assay), and peroxynitrites; thus decreasing the IC50 values to approximately 20, 25, and 20 %, respectively, of the levels attained with the nonhydrolyzed proteins. Metal chelation (HORAC assay) also enhanced respect to isolate levels, but to a lesser extent (decreasing IC50 values to only 50 %). The nitric-oxide- and superoxide-scavenging capacities of the digests were not relevant with respect to the methodologies used. The gastrointestinal digests from amaranth proteins acted against reactive species by different mechanisms, thus indicating the protein isolate to be a potential polyfunctional antioxidant ingredient.
Ozone is a powerful oxidant that presents dual activity: either as a therapeutic or as a toxic agent. The aim of this study was to investigate the effects of intraperitoneal (i.p.) application of ozone on the endogenous antioxidant enzymes of Wistar rats compared with the amendment of the total antioxidant capacity in blood and urine. Rats were divided randomly into two groups: the control group (CG) which was injected with placebo (NaCl 0.9%) and the ozone group (OG) which was administrated daily for 10 consecutive days with ozone at a concentration of 6.3μg/Kg body weight. Blood and urine samples were collected at the beginning, after the administration period and 22 days after the initiation of the experiment. Intraperitoneal application of ozone leads to a potent Increase to glutathione peroxidase (GPx) levels with no effect to Superoxide dismutase (SOD) levels. Total antioxidant capacity (TAC) was significantly decreased in plasma, red blood cells (RBCs) and urine of the rats. Malondialdehyde (MDA) concentration in urine remained stable. To our knowledge these are the first experimental results showing that repeated i.p. application of ozone in low doses produce severe changes to the whole antioxidant capacity of the blood and indications of toxicity, as the organism exert efforts to adapt to oxidative stress.
Anti-carcinogenic potential of hydro-ethanolic extract of Euphorbia neriifolia (EN) leaves and an isolated flavonoid (ENF) was investigated against N-Nitrosodiethylamine (DENA)-induced renal carcinogenesis in mice. Experimental mice were pretreated with 150 and 400 mg/kg body wt of EN, 0.5% and 1% mg/kg body wt of butylated hydroxylanisole (BHA) as a standard antioxidant and 50 mg/kg body wt of ENF for 21 days prior to the administration of a single dose of 50 mg/kg body wt of DENA. Levels of renal markers (urea and creatinine), xenobiotic metabolic enzymes (Cyt P450 and Cyt b5), lipid peroxidation (LPO), antioxidants (SOD, CAT, GST and GSH) and other biochemical parameters--AST, ALT, ALP, total protein (TP), and total cholesterol (TC) were measured to determine the renal carcinogenesis caused by DENA. DENA administration significantly (p < 0.001) decreased the body weight and increased the tissue weight. It significantly (p < 0.001) enhanced the levels of Cyt P450, Cyt b5 and LPO and decreased the levels of SOD, CAT, GST and GSH content. The activities of AST, ALT and ALP and the TP content and renal markers were also significantly decreased (p < 0.001), while TC level was markedly increased after DENA administration, as compared with the normal control group (p < 0.001). Pretreatment with EN and ENF counteracted DENA-induced oxidative stress (LPO) and exerted its protective effects by restoring the levels of antioxidants (SOD, CAT, GST and GSH), biochemical parameters (AST, ALT, ALP, TP and TC), renal markers (urea and creatinine) and xenobiotic enzymes (Cyt P450 and Cyt b5) in renal tissue. In conclusion, the present study showed significant anti-carcinogenic potential of the hydro-ethanolic extract of E. neriifolia and ENF against DENA-induced renal carcinogenicity.
The potential of lipases (E.C.3.1.1.3.) as biocatalysts for the production of fatty acid derivatives for the food and nutraceutical industries, such as flavouring esters, fatty acid esters of antioxidants and structured lipids, is enormous, mainly due to their high regio- and stereo-selectivities, in addition to the other well-known advantages of enzymatic processes. The replacement of chemical catalysts by lipases presents great benefits in terms of the nutritional properties of the obtained products and environmental care. The reactions performed for the production of these compounds, as well as the best operation conditions, the biocatalysts used, reactor types and operation mode, are addressed in this review.
This study investigated the effects of combined supplementation with vitamin E and C against oxidative stress (OS) caused by intermittent cold exposure (ICE) in the hypothalamus (HY) of aging male Wistar rats [adult (3-months), middle-aged (18-months) and old (24-months)]. Each age was divided into sub-groups: control (CON), cold-exposed at 10 °C (C10), cold-exposed at 5 °C (C5), supplemented control (CON+S) and supplemented cold-exposed at either 5 °C (C5+S) or 10 °C (C10+S). The supplement was a daily dose of 400 mg vitamin C and 50 IU of vitamin E/kg body weight. Cold exposure lasted 2 h/day for 4 weeks. All age groups exposed to cold showed increase in body mass and feeding efficiency. Feeding efficiency in the supplemented old group showed a statistically significant increase in the cold (p < 0.001). Age-related increases in levels of hydrogen peroxide (H(2)O(2)), protein carbonyl (PrC), advanced oxidation protein products and thiobarbituric acid reactive substances (TBARS) were further increased by cold in the HY. Cold reduced thiol(P-SH) levels and increased superoxide dismutase (SOD) and, catalase (CAT) activities as well as Hsp72 levels. However, supplementation lowered H(2)O(2), PrC and TBARS with decreases in Hsp72 levels and in SOD and CAT activities. These changes were concomitant with elevations in P-SH, vitamin E and C levels. The results show that the OS caused by ICE in the HY and its subsequent protection following supplementation is related to the intensity of ICE as well as age of the animal. Immunohistochemical studies are underway to examine the findings on ICE-induced oxidative injury in the HY, and the prospects for vitamin E and C supplementation in the senescent.
Oxidative modifications of low-density lipoproteins (LDL) have a determinant role in atherogenesis and the study of agents that can modulate LDL oxidation is of pharmacological and therapeutic significance. Therefore, the aim of this study was to evaluate the antioxidant effect of the disubstituted diaryl diselenides, p-methoxyl-diphenyl diselenide (p-CH(3)O-C(6)H(4)Se)(2) (DM) and p-chloro-diphenyl diselenide (p-Cl-C(6)H(4)Se)(2) (DC), on Cu(2+)-induced LDL oxidation. Both compounds caused a dose-dependent inhibition of human serum and isolated LDL oxidation evidenced by the increasing of the lag phase of lipid peroxidation and decreased the lipid oxidation rate (Vmax). The protein moieties from isolated LDL were also protected from Cu(2+)-induced oxidation. Moreover, the disubstituted diaryl diselenides efficiently decreased the oxidized LDL (ox-LDL) induced foam cell formation in J774A.1 macrophage cells. Mechanistically, we have demonstrated that the antioxidant and antiatherogenic effects of DM and DC are related to formation of their selenol intermediates (RSeH) either by a direct reaction with endogenous thiols (GPx-like activity) or via their reduction by TrxR (using NADPH as electron donor). Considering the powerful effect of DM and DC against LDL-induced toxicity, they could be considered for developing of new therapeutic approaches to preventing and treating atherosclerosis and cardiovascular diseases.
The objective of this study was to investigate the effects of catechin and epicatechin on the activity of the endogenous antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) (as well as the total antioxidant capacity (TAC)) of rats after intra-peritoneal (i.p.) administration.
Twenty-four Wistar rats were randomly divided into two groups: the experimental group which was administered daily with a 1:1 mixture of epicatechin and catechin at a concentration of 23 mg/kg body weight for 10 days and the control group which was injected daily with an equal amount of saline. Blood and urine samples were collected before and after the administration period, as well as 10 days after (follow-up).
Intra-peritoneal administration of catechins led to a potent decrease in GPx levels and a significant increase in SOD levels. TAC was significantly increased in plasma and urine. Malonaldehyde levels in urine remained stable. In the animals treated with catechins, SOD activity showed a moderate negative correlation with GPx activity.
Boosting the activity of the antioxidant enzymes could be a potential adjuvant approach for the treatment of the oxidative stress-related diseases.
A new glyceroglycolipid, ishigoside (1, 2-di-O-palmitoyl-3-O-(6-deoxy-6-amino)-α-D-glucopyranosyl-glycerol, 1), along with two known compounds were isolated from the brown alga Ishige okamurae. The structure of the new compound was determined on the basis of spectroscopic analysis, including 1D and 2D NMR, MS techniques
and chemical methods. Moreover, direct free radical scavenging activities of ishigoside were investigated by electron spin
resonance spectrometry (ESR) technique. The results suggested that ishigoside was a potential free-radical scavenger against
DPPH, hydroxyl, alkyl, and superoxide radicals with the EC50 of 31.2, 16.7, 22.7, and 26.8 μM, respectively.
An enzyme which catalyzes the dismutation of superoxide radicals (O2·⁻ + O2·⁻ + 2H⁺ → O2 + H2O2) has been purified by a simple procedure from bovine erythrocytes. This enzyme, called superoxide dismutase, contains 2 eq of copper per mole of enzyme. The copper may be reversibly removed, and it is required for activity. Superoxide dismutase has been shown to be identical with the previously described copper-containing erythrocuprein (human) and hemocuprein (bovine).
Stable solutions of the superoxide radical were generated by the electrolytic reduction of O2 in an aprotic solvent, dimethylformamide. Slow infusion of such solutions into buffered aqueous media permitted the demonstration that O2·⁻ can reduce ferricytochrome c and tetranitromethane, and that superoxide dismutase, by competing for the superoxide radicals, can markedly inhibit these reactions.
Superoxide dismutase was used to show that the oxidation of epinephrine to adrenochrome by milk xanthine oxidase is mediated by the superoxide radical.
An assay of several tissues indicates that superoxide dismutase is widely distributed within mammalian organisms.
Antioxidants have been proposed to have antiatherogenic potential by their inhibition of low density lipoprotein (LDL) oxidation. Here, we report an antioxidant, BO-653 (2,3-dihydro-5-hydroxy-2,2-dipentyl-4,6-di-tert-butylbenzofuran), designed to exhibit antioxidative potency comparable to that of α-tocopherol, but yet possess a high degree of lipophilicity comparable to that of probucol. BO-653 exhibits a high affinity for LDL and is well distributed in aortic vessels in vivo. In atherosclerosis models of rabbits and mice, BO-653 has been shown to be able to suppress the formation of atherosclerotic lesions without untoward side effects. Specifically, there was no reduction of high density lipoprotein levels. This antioxidant provides additional evidence in support of the oxidized-LDL hypothesis, and itself is a promising candidate antioxidant for clinical use.
We have characterized further the antioxidant responsive element (ARE) identified in the 5'-flanking region of the rat glutathione S-transferase Ya subunit gene and the NAD(P)H:quinone reductase gene by mutational and deletion analyses. Our data suggest that the sequence, 5'-puGTGACNNNGC-3' 3'-pyCACTGNNNCG-5' where N is any nucleotide, represents the core sequence of the ARE required for transcriptional activation by phenolic antioxidants and metabolizable planar aromatic compounds (e.g. beta-naphthoflavone and 3-methylcholanthrene). We also have found that the ARE is responsive to hydrogen peroxide and phenolic antioxidants that undergo redox cycling. These latter data suggest that the ARE is responsive to reactive oxygen species and thus may represent part of a signal transduction pathway that allow eukaryotic cells to sense and respond to oxidative stress.
Superoxide dismutase reduces injury in many disease processes, implicating superoxide anion radical (O2-.) as a toxic species in vivo. A critical target of superoxide may be nitric oxide (NO.) produced by endothelium, macrophages, neutrophils, and brain synaptosomes. Superoxide and NO. are known to rapidly react to form the stable peroxynitrite anion (ONOO-). We have shown that peroxynitrite has a pKa of 7.49 +/- 0.06 at 37 degrees C and rapidly decomposes once protonated with a half-life of 1.9 sec at pH 7.4. Peroxynitrite decomposition generates a strong oxidant with reactivity similar to hydroxyl radical, as assessed by the oxidation of deoxyribose or dimethyl sulfoxide. Product yields indicative of hydroxyl radical were 5.1 +/- 0.1% and 24.3 +/- 1.0%, respectively, of added peroxynitrite. Product formation was not affected by the metal chelator diethyltriaminepentaacetic acid, suggesting that iron was not required to catalyze oxidation. In contrast, desferrioxamine was a potent, competitive inhibitor of peroxynitrite-initiated oxidation because of a direct reaction between desferrioxamine and peroxynitrite rather than by iron chelation. We propose that superoxide dismutase may protect vascular tissue stimulated to produce superoxide and NO. under pathological conditions by preventing the formation of peroxynitrite.
d-alpha-Tocopherol, but not d-beta-tocopherol, negatively regulates proliferation of vascular smooth muscle cells at physiological concentrations. d-alpha-Tocopherol inhibits protein kinase C (PKC) activity, whereas d-beta-tocopherol is ineffective. Furthermore d-beta-tocopherol prevents the inhibition of cell growth and of PKC activity caused by d-alpha-tocopherol. The negative regulation by d-alpha-tocopherol of PKC activity appears to be the cause and not the effect of smooth muscle cell growth inhibition. d-alpha-Tocopherol does not act by binding to PKC directly but presumably by preventing PKC activation. It is concluded that, in vascular smooth muscle cells, d-alpha-tocopherol acts specifically through a nonantioxidant mechanism and exerts a negative control on a signal transduction pathway regulating cell proliferation.
Peroxynitrite, a powerful mutagenic oxidant and nitrating species, is formed by the near diffusion-limited reaction of .NO and O2.- during activation of phagocytes. Chronic inflammation induced by phagocytes is a major contributor to cancer and other degenerative diseases. We examined how gamma-tocopherol (gammaT), the principal form of vitamin E in the United States diet, and alpha-tocopherol (alphaT), the major form in supplements, protect against peroxynitrite-induced lipid oxidation. Lipid hydroperoxide formation in liposomes (but not isolated low-density lipoprotein) exposed to peroxynitrite or the .NO and O2.- generator SIN-1 (3-morpholinosydnonimine) was inhibited more effectively by gammaT than alphaT. More importantly, nitration of gammaT at the nucleophilic 5-position, which proceeded in both liposomes and human low density lipoprotein at yields of approximately 50% and approximately 75%, respectively, was not affected by the presence of alphaT. These results suggest that despite alphaT's action as an antioxidant gammaT is required to effectively remove the peroxynitrite-derived nitrating species. We postulate that gammaT acts in vivo as a trap for membrane-soluble electrophilic nitrogen oxides and other electrophilic mutagens, forming stable carbon-centered adducts through the nucleophilic 5-position, which is blocked in alphaT. Because large doses of dietary alphaT displace gammaT in plasma and other tissues, the current wisdom of vitamin E supplementation with primarily alphaT should be reconsidered.
Selenoprotein P is an extracellular protein containing presumably 10 selenocysteines that are encoded by the UGA stop codon
in the open reading frame of the mRNA. The function of selenoprotein P is currently unknown, although several indirect lines
of evidence suggest that selenoprotein P is a free radical scavenger. We first developed a conventional procedure to isolate
selenoprotein P from human plasma. Next, we investigated the reactivities of selenoprotein P against various hydroperoxides
in the presence of glutathione. Although selenoprotein P reduces neither hydrogen peroxide nor tertiary butyl hydroperoxide,
it does reduce phospholipid hydroperoxide such as 1-palmitoyl-2-(13-hydroperoxy-cis-9,trans-11-octadecadienoyl)-3-phosphatidylcholine hydroperoxide. Kinetic analysis demonstrated atert-uni ping-pong mechanism, similar to those described for classical glutathione peroxidase and phospholipid hydroperoxide glutathione
peroxidase. Not only glutathione, but also dithiothreitol, mercaptoethanol, cysteine, and homocysteine, were effective as
reducing substances, as in the case of phospholipid hydroperoxide glutathione peroxidase. These results show that selenoprotein
P functions as a phospholipid hydroperoxide glutathione peroxidase in extracellular fluids.
The antioxidant activities of α-, β-, γ-, and δ-tocopherols were studied. They were all effective as antioxidant in the oxidations of methyl linoleate in homogeneous solution. When one of the four tocopherols was used alone, they were consumed at the same rate and they suppressed the oxidation for the same period. However, the stabilities of chromanyloxyl radicals derived from the corresponding tocopherols varied considerably and decreased in the order α>β≅γ>δ -chromanyloxyl radicals. α-Tocopherol reacts quite rapidly with β-, γ-, and δ-chromanyloxyl radicals to give α-chromanyloxyl radical and β-, γ-, and δ-tocopherols respectively. Accordingly, when the four tocopherols were used together, α-tocopherol was consumed first, then β- and γ-tocopherols were consumed, and δ-tocopherol began to decrease after most of α-, β-, γ-tocopherols were depleted.
Peroxynitrite, a powerful mutagenic oxidant and nitrating species, is
formed by the near diffusion-limited reaction of \cdot NO and
O2{\cdot} during activation of phagocytes. Chronic
inflammation induced by phagocytes is a major contributor to cancer and
other degenerative diseases. We examined how γ -tocopherol
(γ T), the principal form of vitamin E in the United States diet,
and α -tocopherol (α T), the major form in supplements,
protect against peroxynitrite-induced lipid oxidation. Lipid
hydroperoxide formation in liposomes (but not isolated low-density
lipoprotein) exposed to peroxynitrite or the \cdot NO and
O2{\cdot} generator SIN-1
(3-morpholinosydnonimine) was inhibited more effectively by γ T
than α T. More importantly, nitration of γ T at the
nucleophilic 5-position, which proceeded in both liposomes and human low
density lipoprotein at yields of ≈ 50% and ≈ 75%, respectively,
was not affected by the presence of α T. These results suggest
that despite α T's action as an antioxidant γ T is required
to effectively remove the peroxynitrite-derived nitrating species. We
postulate that γ T acts in vivo as a trap for membrane-soluble
electrophilic nitrogen oxides and other electrophilic mutagens, forming
stable carbon-centered adducts through the nucleophilic 5-position,
which is blocked in α T. Because large doses of dietary α T
displace γ T in plasma and other tissues, the current wisdom of
vitamin E supplementation with primarily α T should be
reconsidered.
2,3-Dihydro-5-hydroxy-2,2-dipentyl-4,6-di-tert-butylbenzofuran (BO-653) is a novel antioxidant designed as a drug for inhibition of lipid peroxidation in vivo. To understand the dynamics of action of BO-653 as an antioxidant, the effects of substituents and side chains on the stability and reactivity of the BO-653 derived radical were studied and compared with the aryloxyl radicals derived from related compounds including α-tocopherol. The rate constants for the reactions of the aryloxyl radicals with themselves, lipid, hydroperoxide, and ascorbate were measured with a stopped-flow electron spin resonance (ESR) spectroscope equipped with a rapid mixing device. The ortho substituents exerted profound effects on the rate of bimolecular decay reactions and the reaction with ascorbic acid, while the effects on the reactions with methyl linoleate and tert-butyl hydroperoxide were much less significant. The side chain at the 2-position did not exert any effect in organic solution but the two pentyl side chains, when compared with two methyl side chains, diminished the apparent reactivities in the liposomal membranes.
The reduction of membrane-bound hydroperoxides is a major factor acting against lipid peroxidation in living systems. This paper presents the characterization of the previously described ‘peroxidation-inhibiting protein’ as a ‘phospholipid hydroperoxide glutathione peroxidase’. The enzyme is a monomer of 23 kDa (SDS-polyacrylamide gel electrophoresis). It contains one gatom Se/22 000 g protein. Se is in the selenol form, as indicated by the inactivation experiments in the presence of iodoacetate under reducing conditions. The glutathione peroxidase activity is essentially the same on different phospholipids enzymatically hydroperoxidized by the use of soybean lipoxidase (EC 1.13.11.12) in the presence of deoxycholate. The kinetic data are compatible with a tert-uni ping-pong mechanism, as in the case of the ‘classical’ glutathione peroxidase (EC 1.11.1.9). The second-order rate constants (K1) for the reaction of the enzyme with the hydroperoxide substrates indicate that, while H2O2 is reduced faster by the glutathione peroxidase, linoleic acid hydroperoxide is reduced faster by the present enzyme. Moreover, the phospholipid hydroperoxides are reduced only by the latter. The dramatic stimulation exerted by Triton X-100 on the reduction of the phospholipid hydroperoxides suggests that this enzyme has an ‘interfacial’ character. The similarity of amino acid composition, Se content and kinetic mechanism, relative to the difference in substrate specificity, indicates that the two enzymes ‘classical’ glutathione peroxidase and phospholipid hydroperoxide glutathione peroxidase are in some way related. The latter is apparently specialized for lipophylic, interface substrates.
Addition of either 2(3)-tert-butyl-4-hydroxyanisole (BHA) or 1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline (ethoxyquin) to the diet greatly decreases the levels of mutagenic metabolites of benzo(a)pyrene in CD-1 mice. The mutagenic activity of the urinary metabolites of benzo(a)pyrene is markedly reduced in the presence of glutathione together with the liver cytosols of rats or fed fid on a diet containing BHA. The liver cytosols of mice and rats maintained on control diets are much less effective in this respect. Dietary BHA causes increases in mouse and rat hepatic glutathione S-transferase (EC 2.5.1.18) specific activities with 1,2-dichloro-4-nitrobenzene, 1-chloro-2,4-dinitrobenzene, p-nitrobenzylchloride, and Δ5-androstene-3,17-dione. In the mouse the increases are larger (5- to 10-fold) and are dependent on the dose and duration of administration of BHA. Increases in these glutathione S-transferase specific activities were also observed in mouse hepatic cytosols after feeding of ethoxyquin. direct addition of reduced glutathione and purified glutathione S-transferases A and B obtained from rat liver to the mutagenicity assay system mimicked the effect of the rodent cytosols. Since BHA and ethoxyquin are known to reduce the neoplastic effects of a variety of potent carcinogens, we suggest that the protective effects of these antioxidants may be accounted for, at least in part, by their ability to elevate the glutathione S-transferases. These enzymes inactivate arene oxides and other hydrophobic electrophiles by catalyzing their conjugation with glutathione.
Administration of the antioxidant 2(3)-tert-butyl-4-hydroxyanisole (BHA) in the diet caused a marked increase in the specific activity of epoxide hydratase (EC 4.2.1.63) in hepatic microsomes of CD-1 mice. The increases in epoxide hydratase activities produced by BHA were far greater (11-fold) than were those produced by the administration of well-known enzyme inducers such as 3-methylcholanthrene, phenobarbital, and Aroclor 1254 (2- to 3-fold). The near-maximal increase in epoxide hydratase activity was observed after feeding of the BHA diet for 3 days. When BHA was administered by gastric intubation, the level of increase was only 75% of that attained by feeding BHA in the diet. The increase in epoxide hydratase activity produced by BHA treatment of Sprague-Dawley rats was not as pronounced (less than 3-fold) as that observed in CD-1 mice.
Errors in the replication of DNA are a major source of spontaneous mutations, and a number of cellular functions are involved in correction of these errors to keep the frequency of spontaneous mutations very low. We report here a novel mechanism which prevents replicational errors by degrading a potent mutagenic substrate for DNA synthesis. This error-avoiding process is catalysed by a protein encoded by the mutT gene of Escherichia coli, mutations of which increase the occurrence of A.T----C.G transversions 100 to 10,000 times the level of the wild type. Spontaneous oxidation of dGTP forms 8-oxo-7,8-dihydro-2'-dGTP (8-oxodGTP), which is inserted opposite dA and dC residues of template DNA with almost equal efficiency, and the MutT protein specifically degrades 8-oxodGTP to the monophosphate. This indicates that elimination from the nucleotide pool of the oxidized form of guanine nucleotide is important for the high fidelity of DNA synthesis.
Superoxide and hydrogen peroxide are reactive oxygen species (ROS) primarily produced by phagocytic cells as a consequence of the process of phagocytosis. This defensive role, may, however, become one of attack when production of ROS is excessive and overwhelms cellular scavenging systems. This happens in situations such as acute inflammation and results in host cell membrane damage, which is particularly prevalent in the presence of transition metal catalysts such as iron and copper. The skin is uniquely vulnerable to this attack being rich in polyunsaturated fatty acids and exposed to high oxygen tensions and ultraviolet light, both of which promote production of ROS. Additionally, the respiratory burst of infiltrating polymorphonuclear leukocytes and macrophages in inflamed skin will produce high local levels of superoxide that can release "catalytic iron" from storage proteins such as ferritin. The role of iron and ROS in the pathogenesis of inflammatory skin disease is discussed as is the possibility of novel therapeutic strategies based on their removal.
Glutathione S-transferase (GST) Ya subunit gene expression is induced in mammalian tissues by two types of chemical agents: (i) planar aromatic compounds (e.g., 3-methylcholanthrene, beta-naphthoflavone, and 2,3,7,8-tetrachlorodibenzo-p- dioxin) and (ii) electrophiles (e.g., trans-4-phenyl-3-buten-2-one and dimethyl fumarate) or compounds easily oxidized to electrophiles (e.g., tert-butylhydroquinone). To study the mechanism of this induction, we have introduced deletions in the 5' flanking region of a mouse GST Ya subunit gene, fused it to the coding sequence for chloramphenicol acetyltransferase (CAT) activity, and transfected the Ya-CAT genes for expression into hepatoma cells. We show that a single cis-regulatory element, between nucleotides -754 and -713 from the start of transcription, is responsible for the induction by both planar aromatic and electrophilic compounds. Using murine hepatoma cell mutants defective in either the Ah-encoded aryl hydrocarbon receptor (BPrc1 mutant) or in cytochrome P1-450 gene (c1 mutant), we show that induction by planar aromatic but not by electrophilic inducers requires a functional Ah receptor and cytochrome P1-450 activity. From this it is concluded that Ya gene activation by planar aromatic compounds involves metabolism of these inducers by the phase I xenobiotic-metabolizing cytochrome P1-450 system into electrophilic compounds, which is consistent with a recently proposed model [Prochaska, H. J. & Talalay, P. (1988) Cancer Res. 48, 4776-4782]. Therefore, the regulatory sequence of the Ya gene should be considered an electrophile-responsive element (EpRE) activated exclusively by inducers containing an electrophilic center. An EpRE-containing 41-bp oligonucleotide ligated at the -187 site of the Ya gene promoter confers upon it an increase in basal activity and xenobiotic inducibility. The basal activity augments with the number of EpRE copies. DNase I protection patterns show the protection of the EpRE domain by a nuclear factor(s) that becomes more abundant upon exposure of Hepa 1c1c7 cells to tert-butylhydroquinone.
Publisher Summary This chapter discusses the role of protein degradation as an index of oxidative stress. Oxygen radicals and other activated oxygen species are known to participate in numerous physiological and pathological processes. Situations that augment oxidant exposure, or compromise antioxidant capacity, are commonly referred to as oxidative stress. Oxidative stress can result from exogenous sources or from increases in endogenous oxidative metabolism. Regardless of its source, oxidative stress has been found to affect the behavior of several different cell types. Protein degradation is apparent immediately (no lag phase) after red blood cells (RBC), muscle cells, or bacteria are treated with an oxidant. The response appears to be linear over at least a 3-hr treatment time. Protein degradation assays provide powerful advantages over other techniques. For example, it is possible to perform amino acid analysis to obtain a more complete profile of products. The assays are inherently more sensitive due to the homogeneity of products formed (i.e., amino acids) and the amplification of signal that fluorescence and radiolabeling techniques provide.
This chapter discusses the phospholipid hydroperoxide glutathione peroxidase (PHGPX) activity in tissues and its purification. PHGPX is the second selenoenzyme discovered in mammals. Because PHGPX is a soluble enzyme has been purified from cell sap, it can be classified as a cytosolic enzyme. However, a substantial activity, which can be partially recovered by high ionic strength extraction, is present in membranes of subcellular organelles. Taking advantage of its peroxidation-inhibiting activity, PHGPX is discovered and purified in a simple lipid peroxidation test. The peroxidase activity, which is first identified on a partially purified preparation of the enzyme, is in fact measurable in crude fractions with some difficulties. Thereafter, the introduction, as peroxide substrate, of mixed micelles of phospholipid hydroperoxides and Triton X-100 greatly simplifies activity measurements. PHGPX activity, although measurable on liposomes or membranes containing hydroperoxides, is higher and linear when the substrate is in micellar form. To search for PHGPX activity in tissues, if activity is low and precise measurements are not possible using homogenates, the chapter uses two preparations, neither of them giving the true “total activity’ present in the tissue. In the first preparation, the tissue is broken in a Polytron homogenizer for 5 min in 3 volumes of 0.1 M Tris-HCl (pH 7.4), 0.3 M KCl, and centrifuged for 15 min at 15,000 g and 45 min at 100,000 g. In the second preparation, the tissue is homogenized in 3 volumes of 0.25 M sucrose, 20 mM Tris-HC1 (pH 7.4).
Unilamellar vesicles (liposomes) consisting of liver phosphatidylcholine and phosphatidylethanolamine were used as model membranes and subjected to lipid peroxidation. Following peroxidation samples were treated with phospholipase A2 from snake venom and subsequently analyzed for products of lipid peroxidation and of phospholipase A2 action. A significantly increased susceptibility to phospholipase A2 was noted for liposomes subjected to peroxidation, as compared to controls, which correlated with the extent of lipid peroxidation measured by the formation of thiobarbituric acid reacting products and conjugated dienes. Low levels of peroxides were detected in control liposomes and these peroxidases were rapidly cleaved by phospholipase A2, such that nearly 40% of the total peroxide content was associated with free fatty acids after l5 min incubation. Oxidized liposomes contained over seven fold the level of lipid peroxidation products, and the were also rapidly cleaved by phospholipase A2 where over 50% were recovered as free fatty acids following l5 min of exposure to phospholipase A2. Along with this high order of removal of oxidized fatty acids, a marked hydrolysis of intact fatty acids was also observed. The extent of fatty acid release was roughly correlated with the degree of fatty acid unsaturation. A substantial increase in the release of arachidonic acid was found when peroxidized membranes were analyzed.
To develop a novel potent radical-scavenging antioxidant, the ideal structure of a phenolic compound was designed considering the factors that determine antioxidant potency. 2,3-Dihydro-5-hydroxy-2,2-dipentyl-4, 6-di-tert-butylbenzofuran (BO-653) was thus synthesized and its antioxidant activity was evaluated against lipid peroxidations in vitro. The electron spin resonance study showed that the phenoxyl radical derived from BO-653 was more stable than alpha-tocopheroxyl radical. BO-653 reduced alpha-tocopheroxyl radical rapidly, but alpha-tocopherol did not reduce the phenoxyl radical derived from BO-653. However, the chemical reactivity of BO-653 toward peroxyl radical was smaller than that of alpha-tocopherol. This was interpreted as the steric effect of bulky tert-butyl groups at both ortho positions which hindered the access of peroxyl radical to the phenolic hydrogen. However, the tertbutyl substituents increased the stability of BO-653 radical and also lipophilicity, and its antioxidant potency against lipid peroxidation in phosphatidylcholine liposomal membranes was superior to that of alpha-tocopherol. Ascorbic acid reduced the phenoxyl radical derived from BO-653 and spared BO-653 during the oxidation of lipid in the homogeneous solution. On the other hand, ascorbic acid did not spare BO-653 in the oxidation of liposomal membranes. It was concluded that BO-653 is a potent novel radical-scavenging antioxidant.
alpha-Tocopherol transfer protein (alphaTTP), a product of the gene which causes familial isolated vitamin E deficiency, plays an important role in determining the plasma vitamin E level. We examined the structural characteristics of vitamin E analogs required for recognition by alphaTTP. Ligand specificity was assessed by evaluating the competition of non-labeled vitamin E analogs and alpha-[3H]tocopherol for transfer between membranes in vitro. Relative affinities (RRR-alpha-tocopherol = 100%) calculated from the degree of competition were as follows: beta-tocopherol, 38%; gamma-tocopherol, 9%; delta-tocopherol, 2%; alpha-tocopherol acetate, 2%; alpha-tocopherol quinone, 2%; SRR-alpha-tocopherol, 11%; alpha-tocotrienol, 12%; trolox, 9%. Interestingly, there was a linear relationship between the relative affinity and the known biological activity obtained from the rat resorption-gestation assay. From these observations, we conclude that the affinity of vitamin E analogs for alphaTTP is one of the critical determinants of their biological activity.
2,3-Dihydro-5-hydroxy-2,2-dipentyl-4,6-di-tert-butyl-benzofuran (BO-653) is a novel antioxidant synthesized by theoretical designing based on the previous experimental findings and consideration. The antioxidant activities of BO-653 against the oxidative modification of low-density lipoprotein (LDL) induced by free radicals were studied. BO-653 was consumed faster than endogenous alpha-tocopherol and inhibited the formation of lipid hydroperoxides, which was observed during the consumption of alpha-tocopherol. Doxyl stearic acids incorporated into LDL as spin probes competed with the antioxidants in scavenging radicals. It was found that the efficacy of radical scavenging by alpha-tocopherol became smaller as the radical went deeper into the interior of LDL particle, whereas that by BO-653 did not change. Ascorbic acid in the aqueous phase spared alpha-tocopherol efficiently during oxidation. On the other hand, the sparing effect of ascorbic acid for BO-653 was not remarkable, unlike that for alpha-tocopherol, which implied different locations of radicals derived from BO-653 and alpha-tocopherol within the LDL particle. It was concluded that BO-653 protected LDL from oxidative modification efficiently by scavenging peroxyl radicals and by reducing alpha-tocopheroxyl radicals and that this novel antioxidant might act as a potent inhibitor of development of atherosclerosis.
It has been proposed (S. Christen et al. Proc. Natl. Acad. Sci. USA 94, 3217-3222, 1997) that although alpha-tocopherol (alpha-TH) is an efficient antioxidant, the presence of gamma-tocopherol (gamma-TH) may be required to scavenge peroxynitrite-derived reactive nitrogen species. To investigate the reactions between alpha-TH, gamma-TH, and peroxynitrite, endogenous levels of both alpha-TH and gamma-TH were monitored when low-density lipoprotein was oxidized in the presence of the peroxynitrite generator 5-amino-3-(4-morpholinyl)-1, 2,3-oxadiazolium (SIN-1). SIN-1 oxidized alpha-TH while gamma-TH levels remained constant. The sparing of gamma-TH was also demonstrated when 1,2-dilauroyl-sn-glycero-3-phosphocholine liposomes containing alpha-TH and gamma-TH were incubated with either SIN-1 or peroxynitrite. Our data show that alpha-TH inhibits peroxynitrite-mediated gamma-TH nitration, i.e., 5-NO2-gamma-tocopherol formation. The rate constants for the reactions between both alpha-TH and gamma-TH with peroxynitrite suggest that the sparing of gamma-TH by alpha-TH does not occur by competitive scavenging, but may be due to the formation of a transient gamma-TH intermediate. Nitration of gamma-TH becomes significant only after alpha-TH levels have been depleted. We conclude alpha-TH alone is sufficient to remove any peroxynitrite-derived reactive nitrogen species, as the presence of alpha-TH attenuates nitration of both gamma-TH and tyrosine. The present results also indicate that a bolus addition of peroxynitrite or SIN-1 to liposomes containing gamma-TH forms 5-NO2-gamma-tocopherol in similar yields. This is in contrast to their reaction profile with tyrosine in aqueous solution. Under these conditions, SIN-1 does not form nitrotyrosine at detectable yields.
We evaluated the effects of alpha-Toc on surface expression of CD11b/CD18 on polymorphonuclear leukocytes (PMN) stimulated with N-formyl-methionyl-leucyl-phenylalanine (fMLP) and oxidized low-density lipoprotein (oxLDL). Incubation of PMN with fMLP (1 microM) or oxLDL (100 microg/mL) increased CD11b/CD18 expression; pretreatment with alpha-Toc reduced in a dose-dependent manner. PMN obtained from healthy adults ingesting 600 mg alpha-Toc per day for 10 days were similarly incubated with fMLP or oxLDL; the surface level of CD11b/CD18 was inversely correlated with serum alpha-Toc concentrations. Adherence of PMN to human umbilical vein endothelial cells was increased by fMLP or oxLDL stimulation but reduced by alpha-Toc pretreatment or anti-CD18 monoclonal antibodies. cAMP-dependent protein kinase (PKA) and protein kinase C (PKC) activity in PMN was also assayed. A PKC inhibitor, but not a PKA inhibitor, suppressed CD11b/CD18 up-regulation, and alpha-Toc slightly decreased fMLP- and oxLDL-induced activation of PKC. These results suggest that alpha-Toc may prevent inflammation by both reducing CD11b/ CD18 up-regulation and decreasing PMN-dependent adherence to EC.
Oxidant stress is associated with diminution of antioxidant molecules, such as alpha-tocopherol. Alpha-tocopherol specifically decreases, in a concentration dependent way, the proliferation of vascular smooth muscle cells. At the same concentrations (10-50 microM) it induces inhibition of protein kinase C (PKC) activity. The latter event is not due to a decrease in PKC level or to alpha-tocopherol binding to PKC, but it results from increase of protein phosphatase 2A1 activity. In vitro data, as well as at a cellular level, demonstrates that protein phosphatase 2A1 is activated, in its trimeric structure--but not as a dimer by alpha-tocopherol. This activation is followed by PKC-alpha dephosphorylation. The activation of protein phosphatase 2A1 and deactivation of PKC-alpha affect the AP1 transcription factor, resulting in a change in the composition and the binding of this factor to DNA. By transfecting smooth muscle cell with a construct containing three TRE (TPA responsive elements), the promoter thymidine kinase and the reporter gene chloramphenicol-acetyl-transferase a modulation of gene expression by alpha-tocopherol is observed. Beta-tocopherol does not cause any of the responses observed with alpha-tocopherol and R,R,R-alpha-tocopherol is twice as potent as all-rac-alpha-tocopherol. When added together, beta-tocopherol prevents the effects of alpha-tocopherol indicating that the mechanism involved is not related to the radical-scavenging properties of these two molecules, which are essentially equal. By differential display analysis it has been found that several genes of smooth muscle cells are differentially transcribed in the presence of alpha-tocopherol but not beta-tocopherol. In particular, the gene of alpha-tropomyosin shows a transient enhancement of transcription as a function of the cell cycle time. Alpha-tropomyosin translation is also increased by alpha-tocopherol and not by beta-tocopherol. Because no changes of mRNA stability can be observed in the presence of alpha-tocopherol, the data supports the conclusion of a transcriptional control exerted by alpha-tocopherol on alpha-tropomyosin. Generally, the data strongly suggests the existence of a ligand/receptor type of mechanism at the basis of alpha-tocopherol action. It is concluded that an oxidative stress-induced diminution of alpha-tocopherol in smooth muscle cell activates a reaction cascade leading to changes in gene expression and increase in cell proliferation by a non-antioxidant mechanism.
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