Antioxidants
See also Oxidation and see neurological diseases and
Antioxidants are a highly effective group of protective agents that act to regulate oxidative reactions. Essentail antioxidants are either endogenous (internally synthesized) or exogenous (consumed). They are often categorized as sacvenger antioxidants and prevention antioxidants.
Scavenger antioxidants remove ROS and include small molecule antioxidants such as water soluble compounds like Vitamin C or glutathione and lipid soluble compounds such as vitamin E, carotenes, lipoic acid and Coenzyme Q. They also include large molecule enzyme antioxidants such as superoxide dismutase (SOD) that detoxifies the superoxide ion, catalase, which deals with hydrogen peroxide and glutatione peroxidase (GPx) which detoxifies cellular peroxides. These enzymes must be synthesized by cells and are subject to genetic and/or macromolecular regulatory mechanisms.
Preventative antioxidants hinder the formation of new ROS. These are proteins that bind ROS to protect essential proteins and include albumin, metallothionine, transferrin, cerulplasmin, and myoglobin.
It is important to note that many of these vitamins do not act in isolation from other antioxidants; rather, they are part of an interlinking set of redox aminoxidant cycles, termed the "antioxidant network." For example, Vitamin E is efficiently reduced from its free radical form (tocotrienoxyl to tocopheroxyl) that arises after quenching lipid radicals to retun back to its native state (tocotrienol and tocopherol) by vitamin C. Vitamin C can regenerate vitamin E directly, while thiol antioxidants, such as glutatione and lipoic acid, can also regenerate vitamin E indirectly via vitamin C.
Oxidative stress is worsened in infection if micronutrients are deficient.
Markers for oxidative stress include 8-hydroxy-2'-deoxyguanosine.
Carotenoids are a class of yellow, orange and red plant derived compounds. All of the more than 600 known carotenoids are antioxidancts and about 50 are vitamins because they have provitamin A activity. Vitamin A refers to preformed retinol and the carotenoids that are coverted to retinol by cleavage of a central bond.
Flavonoids: are naturally occuring plant polyphenols found in abundance in diets rich in fruits, vegetables, and plant-derived beverages such as tea. They are well known to have antioxidant effects. Plant polyphenols have phenol rings that act as electron traps to scavenge peroxy radicals, superoxide anions, and hydroxyl radicals.
The antioxidant effects of tea polyphenols are considered to be associated with their ability to stimulate antioxidant defense metabolism through the redox-regulated transcription factors and mitogen-activated protein kinases (MAPK)-dependent cell cycle regulation.
--cranberry falvonoid contain anthocyanins and favonols, and have been found useful in the imimune response to oxidize low-density lipoprotein (LDL) and its uptake by endothelial macropahges.
-Chili peppers are a food item found with many essential nturietns such as vitamin C, provitimains A and E and several B vitamins.
Vitamin C (ascorbic acid): is water soluble and acts as a cofactor in hydroxylation reactions, which are required for collagen synthesis. It is an essential water-soluble nutrient which primarily exerts its effect on host defense mechanisms and immune homeostatsis by being the most important physiological antioxidant. It is also involved in a variety of other biochemical functions such as hormone synthesis, wound healing, and iron absorption.Vitamin C has been shown to inactivate a host of viruses upon exposure. It has been implicated as hoaving both a preventative and a therapeutic role in a variety of diseases including scurvy, viral infections and common cold, cancer and atherosclerosis.It also protects neutrophils from oxidation.
Part of vitamin C's protective benefit is due to its antioxidant action. Oxidative stress increases the antioxidant requirements of the white blood cell macrophages and lymphyoctes. Vitamin C supplementation increases antioxidant glutathione concentration in lymphocytes and normalizes monocyte adhesion to endothelial cells. Oxidative damage plays a key role in endotoxin (LPS)-induced spesis leading to an inappropriate activation of the transcription factor NFkB and, subsequently, to an overexpression of inflammatory proteins. Vitamin C may protect from dysregulation of the immune-inflammatory response by its antioxidant properties. Long used against the common cold, vitamin C has shown mixed results. However, a 2002 study involving 180 British subjects found supplementation could prevent the common cold, as well as limit severe symptoms and shorten the duration.
Fourt independent double-blind studies have reported that ascorbic acid reguraly ingested in dialy amounts more than 100 mg decreases the incidence as well as the severity of colds in comparison with a placebo.
During active infection this nutreint is quickly depleted thus increasing the body's need. The current RDI is 60 mg. Food sources include citrus fruits, strawberries, mellons, tomatoes, broccoli and peppers. The body's rate of absorption of Vitaimn C is often not greater than 1 g hour, so divided doeses are important. Second, if taking large doeses, rebound scurvy can develop if the individual abruptly stops taking the vitamin.
Vitamin E was discovered as a mcironutrient that is indispensable for reproduction in female rates. In humans, vitamin E deficiency can result in various neurological lesions.
Vitamin E is a fat soluble, like vitaimin A, and composed of a family of 8 related compounds, the tocopherols and tocotrienols. Vitamin E is a strong antioxidant that can support monocyte/macrophage mediated responses. Vitamin E can scavenge free radicals. It is considered one of the most potent fat soluble antioxidants due to its ability to donate electrons, hence interfering with the damaging effects of the oxidation process. It is needed in immune function and supplementation enhances cell mediated immunity in elderly patients. Research shown it plays an important role in the differentiation of immature T cells in the thymus, inducing higher differentiation that results in improved cellular immunity.
Vitmain E influances T cell function by downmodulating prostaglandin E2 in elderly subjects.
Viramin E can decrease serum levels of TNF-alpha and protein kinase C. TNF-alpha incdreases the activity of phospholipase A2. In monocytes, phospholipase A2 stimulates the replicaiton of HIV.
When supplementing with vitamin E, one should always consider selenium since these two nturients act synergistically.
The current RDI is 20 mg. Major dietary sources include salid oils, margarine, legumes and nuts. The immunostimulating effect of vitamin E can usually be acheived by administering 200-800 mg of vitamin E daily. Vitamin E reduces hydrogen peroxide which is used especially by neutrophils to kill microorganisms. So that excessively high use could reduce bactericidal and proliferative activity of periopheral leukocytes.
