![]() ![]() These agents may show specific toxicity towards cancer cells because of the low level of antioxidant defenses found in tumors. These include adriamycin and other anthracyclines, bleomycin, and cisplatin. Several important anticancer agents both bind to DNA and generate reactive oxygen species. However, less data is available for other dietary antioxidants, such as polyphenol antioxidants, zinc, and vitamin E. The relative importance of the antioxidant and pro-oxidant activities of antioxidant vitamins are an area of current research, but vitamin C, for example, appears to have a mostly antioxidant action in the body. The metal ion in this reaction can be reduced, oxidized, and then re-reduced, in a process called redox cycling that can generate reactive oxygen species. + 2 OH − 2 Fe 3+ + Ascorbate → 2 Fe 2+ + Dehydroascorbate.Vitamin C has antioxidant activity when it reduces oxidizing substances such as hydrogen peroxide, however, it can also reduce metal ions which leads to the generation of free radicals through the Fenton reaction. Vitamins that are reducing agents can be pro-oxidants. It may be that oxidative stress produced by such agents mimics a normal physiological signal for fibroblast conversion to myofibroblasts. The pulmonary fibrosis produced by paraquat and the antitumor agent bleomycin is also thought to be induced by the pro-oxidant properties of these agents. Liver cirrhosis is also a major symptom of Wilson's disease. ![]() E.g., interocular copper or vitreous chalicosis is associated with severe vitreous fibrosis, as is interocular iron. Fibrosis įibrosis or scar formation is another pro-oxidant-related symptom. Paraquat also produces parkinsonian-like symptoms in rodents. The pro-oxidant herbicide paraquat, Wilson's disease, and striatal iron have similarly been linked to human Parkinsonism. Thus, all are occasional symptoms of (e.g) hemochromatosis, another name for which is "bronze diabetes". Such syndromes tend to be associated with a common symptomology. Similarly, Wilson's disease is associated with elevated tissue levels of copper. Another disease associated with the chronic presence of a pro-oxidant transition-series metal is hemochromatosis, associated with elevated iron levels. For example, chronic manganism is a classic "pro-oxidant" disease. Transition metals can serve as pro-oxidants. This reduced metal then transfers the single electron to molecular oxygen or peroxide. As a result, the reduction of oxygen typically involves either the initial formation of singlet oxygen, or spin–orbit coupling through a reduction of a transition-series metal such as manganese, iron, or copper. This greatly reduces the rates of these reactions, thus allowing aerobic life to exist. While thermodynamically very favored, reduction of molecular oxygen or peroxide to superoxide or hydroxyl radical respectively is spin forbidden. Some of the conditions that are important include the concentration of the chemical and if oxygen or transition metals are present. Some substances can serve as either antioxidants or pro-oxidants, depending on conditions. The oxidative stress produced by these chemicals can damage cells and tissues, for example an overdose of the analgesic paracetamol (acetaminophen) can fatally damage the liver, partly through its production of reactive oxygen species. Pro-oxidants are chemicals that induce oxidative stress, either by generating reactive oxygen species or by inhibiting antioxidant systems. ![]()
0 Comments
Leave a Reply. |