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      The isoprostanes

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      Biochemical Pharmacology
      Elsevier BV

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          Dietary carcinogens and anticarcinogens. Oxygen radicals and degenerative diseases.

          B. N. Ames (1983)
          The human diet contains a great variety of natural mutagens and carcinogens, as well as many natural antimutagens and anticarcinogens. Many of these mutagens and carcinogens may act through the generation of oxygen radicals. Oxygen radicals may also play a major role as endogenous initiators of degenerative processes, such as DNA damage and mutation (and promotion), that may be related to cancer, heart disease, and aging. Dietary intake of natural antioxidants could be an important aspect of the body's defense mechanism against these agents. Many antioxidants are being identified as anticarcinogens. Characterizing and optimizing such defense systems may be an important part of a strategy of minimizing cancer and other age-related diseases.
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            Free-radical chemistry of cigarette smoke and its toxicological implications.

            Cigarette smoke contains two very different populations of free radicals, one in the tar and one in the gas phase. The tar phase contains several relatively stable free radicals; we have identified the principal radical as a quinone/hydroquinone (Q/QH2) complex held in the tarry matrix. We suggest that this Q/QH2 polymer is an active redox system that is capable of reducing molecular oxygen to produce superoxide, eventually leading to hydrogen peroxide and hydroxyl radicals. In addition, we have shown that the principal radical in tar reacts with DNA in vitro, possibly by covalent binding. The gas phase of cigarette smoke contains small oxygen- and carbon-centered radicals that are much more reactive than are the tar-phase radicals. These gas-phase radicals do not arise in the flame, but rather are produced in a steady state by the oxidation of NO to NO2, which then reacts with reactive species in smoke such as isoprene. We suggest that these radicals and the metastable products derived from these radical reactions may be responsible for the inactivation of alpha 1-proteinase inhibitor by fresh smoke. Cigarette smoke oxidizes thiols to disulfides; we suggest the active oxidants are NO and NO2. The effects of smoke on lipid peroxidation are complex, and this is discussed. We also discuss the toxicological implications for the radicals in smoke in terms of a number of radical-mediated disease processes, including emphysema and cancer.
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              Increase in circulating products of lipid peroxidation (F2-isoprostanes) in smokers. Smoking as a cause of oxidative damage.

              It has been hypothesized that the pathogenesis of diseases induced by cigarette smoking involves oxidative damage by free radicals. However, definitive evidence that smoking causes the oxidative modification of target molecules in vivo is lacking. We conducted a study to determine whether the production of F2-isoprostanes, which are novel products of lipid peroxidation, is enhanced in persons who smoke. We measured the levels of free F2-isoprostanes in plasma, the levels of F2-isoprostanes esterified to plasma lipids, and the urinary excretion of metabolites of F2-isoprostanes in 10 smokers and 10 nonsmokers matched for age and sex. The short-term effects of smoking (three cigarettes smoked over 30 minutes) and the effects of two weeks of abstinence from smoking on levels of F2-isoprostanes in the circulation were also determined in the smokers. Plasma levels of free and esterified F2-isoprostanes were significantly higher in the smokers (242 +/- 147 and 574 +/- 217 pmol per liter, respectively) than in the nonsmokers (103 +/- 19 and 345 +/- 65 pmol per liter; P = 0.02 for free F2-isoprostanes and P = 0.03 for esterified F2-isoprostanes). Smoking had no short-term effects on the circulating levels of F2-isoprostanes. However, the levels of free and esterified F2-isoprostanes fell significantly after two weeks of abstinence from smoking (250 +/- 156 and 624 +/- 214 pmol per liter, respectively, before the cessation of smoking, as compared with 156 +/- 67 and 469 +/- 108 pmol per liter after two weeks' cessation; P = 0.03 for free F2-isoprostanes and P = 0.02 for esterified F2-isoprostanes). The increased levels of F2-isoprostanes in the circulation of persons who smoke support the hypothesis that smoking can cause the oxidative modification of important biologic molecules in vivo.
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                Author and article information

                Journal
                Biochemical Pharmacology
                Biochemical Pharmacology
                Elsevier BV
                00062952
                January 1996
                January 1996
                : 51
                : 1
                : 1-9
                Article
                10.1016/0006-2952(95)02072-1
                f0f3128c-5b5b-4d36-9e49-b6b0b10eb820
                © 1996

                http://www.elsevier.com/tdm/userlicense/1.0/

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