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Exogenous Antioxidants—Double-Edged Swords in Cellular Redox State: Health Beneficial Effects at Physiologic Doses versus Deleterious Effects at High Doses  [PDF]
Jaouad Bouayed,Torsten Bohn
Oxidative Medicine and Cellular Longevity , 2010, DOI: 10.4161/oxim.3.4.12858
Abstract: The balance between oxidation and antioxidation is believed to be critical in maintaining healthy biological systems. Under physiological conditions, the human antioxidative defense system including e.g., superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH) and others, allows the elimination of excess reactive oxygen species (ROS) including, among others superoxide anions (O2.-), hydroxyl radicals (OH.), alkoxyl radicals (RO.) and peroxyradicals (ROO.). However, our endogenous antioxidant defense systems are incomplete without exogenous originating reducing compounds such as vitamin C, vitamin E, carotenoids and polyphenols, playing an essential role in many antioxidant mechanisms in living organisms. Therefore, there is continuous demand for exogenous antioxidants in order to prevent oxidative stress, representing a disequilibrium redox state in favor of oxidation. However, high doses of isolated compounds may be toxic, owing to prooxidative effects at high concentrations or their potential to react with beneficial concentrations of ROS normally present at physiological conditions that are required for optimal cellular functioning. This review aims to examine the double-edged effects of dietary originating antioxidants with a focus on the most abundant compounds, especially polyphenols, vitamin C, vitamin E and carotenoids. Different approaches to enrich our body with exogenous antioxidants such as via synthetic antioxidants, diets rich in fruits and vegetables and taking supplements will be reviewed and experimental and epidemiological evidences discussed, highlighting that antioxidants at physiological doses are generally safe, exhibiting interesting health beneficial effects.
Exogenous Antioxidants—Double-Edged Swords in Cellular Redox State: Health Beneficial Effects at Physiologic Doses versus Deleterious Effects at High Doses  [PDF]
Jaouad Bouayed,Torsten Bohn
Oxidative Medicine and Cellular Longevity , 2010, DOI: 10.4161/oxim.3.4.12858
Abstract: The balance between oxidation and antioxidation is believed to be critical in maintaining healthy biological systems. Under physiological conditions, the human antioxidative defense system including e.g., superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH) and others, allows the elimination of excess reactive oxygen species (ROS) including, among others superoxide anions (O2.-), hydroxyl radicals (OH.), alkoxyl radicals (RO.) and peroxyradicals (ROO.). However, our endogenous antioxidant defense systems are incomplete without exogenous originating reducing compounds such as vitamin C, vitamin E, carotenoids and polyphenols, playing an essential role in many antioxidant mechanisms in living organisms. Therefore, there is continuous demand for exogenous antioxidants in order to prevent oxidative stress, representing a disequilibrium redox state in favor of oxidation. However, high doses of isolated compounds may be toxic, owing to prooxidative effects at high concentrations or their potential to react with beneficial concentrations of ROS normally present at physiological conditions that are required for optimal cellular functioning. This review aims to examine the double-edged effects of dietary originating antioxidants with a focus on the most abundant compounds, especially polyphenols, vitamin C, vitamin E and carotenoids. Different approaches to enrich our body with exogenous antioxidants such as via synthetic antioxidants, diets rich in fruits and vegetables and taking supplements will be reviewed and experimental and epidemiological evidences discussed, highlighting that antioxidants at physiological doses are generally safe, exhibiting interesting health beneficial effects.
Free Radicals, Antioxidants in Disease and Health
Lien Ai Pham-Huy,Hua He,Chuong Pham-Huyc
International Journal of Biomedical Science , 2008,
Abstract: Free radicals and oxidants play a dual role as both toxic and beneficial compounds, since they can be either harmful or helpful to the body. They are produced either from normal cell metabolisms in situ or from external sources (pollution, cigarette smoke, radiation, medication). When an overload of free radicals cannot gradually be destroyed, their accumulation in the body generates a phenomenon called oxidative stress. This process plays a major part in the development of chronic and degenerative illness such as cancer, autoimmune disorders, aging, cataract, rheumatoid arthritis, cardiovascular and neurodegenerative diseases. The human body has several mechanisms to counteract oxidative stress by producing antioxidants, which are either naturally produced in situ, or externally supplied through foods and/or supplements. This mini-review deals with the taxonomy, the mechanisms of formation and catabolism of the free radicals, it examines their beneficial and deleterious effects on cellular activities, it highlights the potential role of the antioxidants in preventing and repairing damages caused by oxidative stress, and it discusses the antioxidant supplementation in health maintenance.
Significance of Dietary Antioxidants for Health  [PDF]
Michael H. Gordon
International Journal of Molecular Sciences , 2012, DOI: 10.3390/ijms13010173
Abstract: Since evidence became available that free radicals were involved in mechanisms for the development of major diseases, including cardiovascular disease and cancer, there has been considerable research into the properties of natural dietary antioxidants. However, it has become clear that dietary antioxidants can only have beneficial effects in vivo by radical scavenging or effects on redox potential if they are present in tissues or bodily fluids at sufficient concentrations. For many dietary components, absorption is limited or metabolism into derivatives reduces the antioxidant capacity. For many dietary phytochemicals, direct antioxidant effects may be less important for health than other effects including effects on cell signalling or gene expression in vivo.
Antioxidants: Their Role in Health and Disease
Sheikh Arshad Saeed,Mian Zainul Sajadeen Urfy,Talaha Mubarak Ali,, Farhad Wazirali Khimani
International Journal of Pharmacology , 2005,
Abstract: During the past few years there has been an escalation of interest in the role of antioxidants in health and disease. Antioxidants act as free radical scavengers and can thus play significant protective role in many age-related and chronic inflammatory diseases. This article reviews the role of antioxidants vitamin C, E and -carotene in the process of ageing and diseases like coronary heart disease, Alzheimer`s disease and cancer. The phenomenon of ageing has been mystery for mankind since long. Naturally occurring antioxidants can help slow this process by preventing us from harmful effects of ageing. The diet of healthy centenarians also shows high intake of antioxidants like vitamin A, C and E. On the other hand lipid peroxidation is necessary for atheroma formation in coronary arteries leading to heart attacks. This process begins early in childhood. By taking antioxidants this process can be significantly slowed down or even terminated. Reactive oxygen species may also lead to DNA changes and gene mutations, a primary pathology behind uncontrolled cell proliferation and tumorigenesis. Vitamin A and E reduce this stress and have been shown to decrease the risk of prostate and gastric cancers. Dementia and Alzheimer`s affects a large proportion of elderly population. These are a result of oxidative damage going on in our brain from our early life. Antioxidants also contribute in preventing these neurodegenerative processes and may improve the standard of living of the elderly.
Dietary Antioxidants and Good Health  [cached]
Kiran Kapoor,Vishal. R. Tandon,B. Kapoor
Pharmaceutical Reviews , 2005,
Abstract: The role of oxidative stress is well recognized now in numerous pathological states, where antioxidants can play very important role. Recent studies provide evidences that low levels of antioxidants are associated with increased risk for many pathological states and that increased intake appears to be protective. However, there are conflicting studies also, that question the rationale for synthetic antioxidant supplementation in these conditions by suggesting detrimental effects to the health. Suicidal oxidative stress produced by some of the antioxidants under certain circumstances remains the major cause of concern, as many antioxidants can act as pro-oxidants in certain conditions.Moreover, at present there are number of unanswered questions associated with practical application of synthetic antioxidant therapy like appropriate timing of administration, dose & duration of therapy, which still need to be determined. Thus, under the shadow of these concerns, the supplementation of natural dietary antioxidant resources seems to be a safe and effective approach currently. In recent times many dietary factors have been recognized to possess antioxidant action and are useful in many pathological conditions because of their antioxidant actions.1The therapeutic potentials of these antioxidant dietary factors have been reviewed in this review article.
Free radicals, oxidative stress and importance of antioxidants in human health  [PDF]
Amit Kunwar,K.I. Priyadarsini
Journal of Medical and Allied Sciences , 2011,
Abstract: Reactive oxygen species (ROS) is a collective term used for oxygen containing free radicals, depending on their reactivity and oxidizing ability. ROS participate in a variety of chemical reactions with biomolecules leading to a pathological condition known as oxidative stress. Antioxidants are employed to protect biomolecules from the damaging effects of such ROS. In the beginning, antioxidant research was mainly aimed at understanding free radical reactions of ROS with antioxidants employing biochemical assays and kinetic methods. Later on, studies began to be directed to monitor the ability of anti-oxidants to modulate cellular signaling proteins like receptors, secondary messengers, transcription factors, etc. Of late several studies have indicated that antioxidants can also have deleterious effects on human health depending on dosage and bio-availability. It is therefore, necessary to validate the utility of antioxidants in improvement of human health in order to take full advantage of their therapeutic potential.
Telomere Recombination Accelerates Cellular Aging in Saccharomyces cerevisiae  [PDF]
Xiao-Fen Chen,Fei-Long Meng,Jin-Qiu Zhou
PLOS Genetics , 2009, DOI: 10.1371/journal.pgen.1000535
Abstract: Telomeres are nucleoprotein structures located at the linear ends of eukaryotic chromosomes. Telomere integrity is required for cell proliferation and survival. Although the vast majority of eukaryotic species use telomerase as a primary means for telomere maintenance, a few species can use recombination or retrotransposon-mediated maintenance pathways. Since Saccharomyces cerevisiae can use both telomerase and recombination to replicate telomeres, budding yeast provides a useful system with which to examine the evolutionary advantages of telomerase and recombination in preserving an organism or cell under natural selection. In this study, we examined the life span in telomerase-null, post-senescent type II survivors that have employed homologous recombination to replicate their telomeres. Type II recombination survivors stably maintained chromosomal integrity but exhibited a significantly reduced replicative life span. Normal patterns of cell morphology at the end of a replicative life span and aging-dependent sterility were observed in telomerase-null type II survivors, suggesting the type II survivors aged prematurely in a manner that is phenotypically consistent with that of wild-type senescent cells. The shortened life span of type II survivors was extended by calorie restriction or TOR1 deletion, but not by Fob1p inactivation or Sir2p over-expression. Intriguingly, rDNA recombination was decreased in type II survivors, indicating that the premature aging of type II survivors was not caused by an increase in extra-chromosomal rDNA circle accumulation. Reintroduction of telomerase activity immediately restored the replicative life span of type II survivors despite their heterogeneous telomeres. These results suggest that telomere recombination accelerates cellular aging in telomerase-null type II survivors and that telomerase is likely a superior telomere maintenance pathway in sustaining yeast replicative life span.
Health Promotion by Antioxidants  [PDF]
Hoyoku Nishino,Michiaki Murakoshi,Yoshiko Satomi
Functional Foods in Health and Disease , 2011,
Abstract: ABSTRACT:Background: Various antioxidnats from daily foods are expected to prevent lifestyle-related diseases. For example, natural carotenoid beta-cryptoxanthin seems to be a promising antioxidant, and based upon epidemiological data it was shown to be a possible cancer preventing agent. For this reason, we chose to study beta-cryptoxanthin more extensively.Methods and Results: From the result of clinical trial using beta-cryptoxanthin-enriched Mandarin orange juice, it was proven to potentiate the preventive activity of multi-carotenoid mixture against liver cancer in the patients with chronic viral hepatitis-induced liver cirrhosis. Furthermore, beta-cryptoxanthin also has preventive activity against alcohol-induced gamma-GTP elevation, and obesity.Conclusion: An antioxidant beta -cryptoxanthin seems to be valuable for health promotion.
Nonheritable Cellular Variability Accelerates the Evolutionary Processes of Cancer  [PDF]
Steven A. Frank,Marsha Rich Rosner
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1001296
Abstract: Recent cancer studies emphasize that genetic and heritable epigenetic changes drive the evolutionary rate of cancer progression and drug resistance. We discuss the ways in which nonheritable aspects of cellular variability may significantly increase evolutionary rate. Nonheritable variability arises by stochastic fluctuations in cells and by physiological responses of cells to the environment. New approaches to drug design may be required to control nonheritable variability and the evolution of resistance to chemotherapy.
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