Vitamin superoxide formation

Vorobjeva LI and Kozyreva LF (1967) Influence of temperature on vitamin B12 formation by Propionibacterium shennanii. Vestn Mosk Univ Biol 52-54 Vorobjeva LI and Kraeva NI (1982) Superoxide radicals and antiradical defence of propionic acid bacteria. Arch Microbiol 133 110-113... 

Vitamin A (retinol) is not a classic antioxidant although it is frequently related to a group of antioxidant vitamins E, C, and A. Murata and Kawanishi [83] found that retinol and its derivative retinal induced the formation of 8-HOdG in HL-60 cells. This process was supposedly mediated by hydroxyl radicals formed from hydrogen peroxide (the product of superoxide dismutation) and endogenous transition metal ions. 

Plasma malondialdehyde-like material, an indicator of lipid peroxidation, is increased in conditions of ischaemia, such as stroke [83, 84] and myocardial infarction [85]. Mitochondria extracted from hearts of vitamin-E-deficient rabbits showed a decreased mitochondrial function and an increased formation of oxygen radicals associated with a reduced superoxide dismutase activity. This was partially reversed by addition of vitamin E in vitro [86]. Measurement of in vitro susceptibility to lipid peroxidation in cardiac muscle from vitamin-E-deficient mice showed a highly significant negative correlation between the concentration of vitamin E and in vitro lipid peroxidation. The results indicate that short-term vitamin E deficiency may expose cardiac muscle to peroxidation injuries [ 87 ]. In rats, treatment for 2 days with isoprenaline increased lipid peroxide activity, as measured by malondialdehyde levels, in the myocardium. Vitamin-E-deficient animals were even more sensitive to this effect, and pretreatment with a-tocopheryl acetate for 2 weeks prevented the effect induced by isoprenaline. The authors [88] propose that free-radical-mediated increases in lipid peroxide activity may have a role in catecholamine-induced heart disease. 

An increased incidence of infection, even sepsis after intramuscular injection, as an adverse effect of megadose vitamin E therapy in very low birth weight infants was first reported in Japan in 1986 (SEDA-12, 330). In a review of the literature in 1992 it was concluded that pharmacological serum concentrations of vitamin E might predispose premature infants to infectious complications, possibly caused by an inhibitory effect of vitamin E on the formation of superoxide anion in leukocytes (27). 

Physiological Function. The mechanism by which L-ascorbic acid benefits an insect is unknown. The vitamin is found in many tissues where it probably plays a variety of roles related to its redox potential. Besides the possible general function of detoxifying superoxide and hydrogen peroxide, L-ascorbic acid may be involved in metabolic processes such as tyrosine metabolism, collagen formation, steroid synthesis, detoxification reactions, phagostimulation, or neuromodulation. At this time one can only speculate about the function of vitamin C in some specific tissues. 

As acute strenuous exercise and chronic exercise training increase the requirement for various antioxidants, it is conceivable that dietary supplementation of specific antioxidants would be beneficial. Older subjects may be more susceptible to oxidative stress and may benefit from the antioxidant protection provided by vitamin E. During severe oxidative stress such as strenuous exercise, the enzymatic and nonenzymatic antioxidant systems of skeletal muscle are not able to cope with the massive free-radical formation, which results in an increase in lipid peroxidation. Vitamin E decreases exercise-induced lipid peroxidation. The exercise may increase superoxide anion generation in the heart, and the increase in the activity of superoxide dismutase (SOD) in skeletal muscle may be... 

In Chapter 9, we saw that vitamin C is used in diverse ways, united only by the same molecular action. This also applies to SOD, catalase or haem oxygenase. At the molecular level, their actions are always identical. The effects, however, are diverse and may serve quite different purposes. Take SOD. Its action is simple to remove superoxide radicals. But is this purely and simply an antioxidant action, or is it also a signal If the formation of superoxide radicals outstrips their removal by SOD, some of the extra free radicals will oxidize the thiol groups in proteins, sending tran-scription factors scurrying to the nucleus. In the nucleus, these transcrip-tion factors bind to DNA and stimulate the production of new proteins, which help restore the cell to health. In other words, the cell adapts to a small change in circumstances, such as a slight increase in oxidative... 

---