Regulations antioxidants

Fig. 2.2 Simplified scheme of oxidant/antioxidant regulation ofNF-KB activation. Different stimuli, leading to an increase of ROS generation inside the ceU, activate the phosphorylation of IkB inhibitory protein and the subsequent proteolysis. Thioredoxin (Trx) may reduce activated NF-kB proteins facilitating nuclear translocation.Qnce released from IkB, the NF-kB complex translocates into the nucleus and the binding to DNA domain in the promoters and enhancers of genes such as TNF-a, IL-1, proliferation and chemotactic factors, adhesion molecule. Some of these genes, in turn, may further induce NF-kB activation, leading to a vicious circle if the regulatory cellular system escapes from...

Antioxidant, regulation of intracellular oxidation-reduction potentials, hydroxylation reactions that require copper or iron... 

Dhakshinamoorthy, S., Long, D.J., II, and Jaiswal, A.K., Antioxidant regulation of genes encoding enzymes that detoxify xenobiotics and carcinogens, Curr. Top. Cell Regul, 36, 201-216, 2000. 

Prestera, T. and Talalay, P, Electrophile and antioxidant regulation of enzymes that detoxify carcinogens, PNAS, 92, 8965-8969, 1995. 

C, ascorbate Water-Soluble Vitamins Antioxidant, regulation of intracellular... 

Prestera T, Talalay P, Alam J, Ahn Yl, Lee PJ, Choi AM. Parallel induction of heme oxygenase-i and chemoprotective phase 2 enzymes by electrophiles and antioxidants regulation by upstream antioxidant-responsive elements (ARE). Mol Med 1995 1 827-837. 

There are numerous synthetic and natural compounds called antioxidants which regulate or block oxidative reactions by quenching free radicals or by preventing free-radical formation. Vitamins A, C, and E and the mineral selenium are common antioxidants occurring naturally in foods (104,105). A broad range of flavonoid or phenoHc compounds have been found to be functional antioxidants in numerous test systems (106—108). The antioxidant properties of tea flavonoids have been characterized using models of chemical and biological oxidation reactions. 

A number of antioxidants have been accepted by the FDA as indirect additives for polymers used in food appHcations. Acceptance is deterrnined by subchronic or chronic toxicity in more than one animal species and by the concentration expected in the diet, based on the amount of the additive extracted from the polymer by typical foods or solvents that simulate food in their extractive effects. Only materials of insignificant risk to the consumer are regulated by the FDA for use in plastics contacted by food stuffs. 

The term vitamin E describes a family of eight antioxidants, four tocopherols, alpha (a), beta ((3), gamma (y) and delta (8), and four tocotrienols (also a, (3, y, and 8). a-Tocopherol is present in nature in only one form, RRR a-tocopherol. The chemical synthesis of a-tocopherol results in eight different forms (SRR, SSR, SRS, SSS, RSR, RRS, RSS, RRR), only one of which is RRR a-tocopherol. These forms differ in that they can be right (R) or left (S) at three different places in the a-tocopherol molecule. RRR a-tocopherol is the only form of vitamin E that is actively maintained in the human body and is therefore the form of vitamin E found in the largest quantities in the blood and tissue. A protein synthesized in the liver (a-TTP alpha-tocopherol transfer protein) preferentially selects the natural form of vitamin E (RRR a-tocopherol) for distribution to the tissues. However, the mechanisms for the regulation of vitamin E in tissues are not known... 

Gene regulation by tocopherols has mainly been associated with PKC because of its deactivation by a-tocopherol and its contribution in the regulation of a number of transcription factors (NF-kappaB, API). A direct participation of the pregnane X receptor (PXR)/ retinoid X receptor (RXR) has been also shown. The antioxidant-responsive element (ARE) and the TGF-beta-responsive element appear in some cases to be implicated as well. The obser ved immunmodulatory function of a-tocopherol may also be attributed to the fact that the release of the proinflammatory cytokine interlukin-l 3 can be inhibited by a-tocopherol via... 

A Retinol, p-carotene Visual pigments in the retina regulation of gene expression and cell differentiation p-carotene is an antioxidant Night blindness, xerophthalmia keratinization of skin... 

Partch, C. L. et al., Postranslational regulation of mammalian circadian clock by cryptochrome and proteinphosphatase 5, Proc Aarf Acad. Sci. USA, 103, 10467, 2006. Briggs, W.R., Christie, J.M., and Salomon, M., Phototropins a new family of flavinbinding blue light receptors in plants, Antioxid. Redox Signal, 3, 775, 2001. Briggs,W.R. et al.. The phototropin family of photoreceptors. Plant Cell, 13, 993, 2001. 

It is possible that dietary flavonoids participate in the regulation of cellular function independent of their antioxidant properties. Other non-antioxidant direct effects reported include inhibition of prooxidant enzymes (xanthine oxidase, NAD(P)H oxidase, lipoxygenases), induction of antioxidant enzymes (superoxide dismutase, gluthathione peroxidase, glutathione S-transferase), and inhibition of redox-sensitive transcription factors. 

Human chronic inflammatory diseases are characterized by populations of cells with altered regulation and function. A large body of evidence suggests that many of these cellular abnormalities may be linked to an increase in the production of free radicals and/or deficiencies of antioxidant defence systems. Oxygen free radicals attack cell structures, altering their function, and are cytotoxic. They have therefore been implicated in the pathogenesis of rheumatoid arthritis as well as many other human diseases (HaUiwell, 1991). 

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