Cholesterol hydroperoxide

As mentioned previously, in the AMD retina iron metabolism is compromised (He et al., 2007 Wong et al., 2007). Thus, it is of interest to determine the effects of potential antioxidants in the presence of iron. In an in vitro study of ARPE-19 cells, addition of a lipophilic iron complex led to about a ninefold increase in the photosensitized yield of 7a,(3-cholesterol hydroperoxides (Wrona et al., 2004). In the presence of the iron, ascorbate exerted pro-oxidant effects, while the effects of a-tocopherol, zeaxanthin, or their combination were still protective (Wrona et al., 2004). Thus, it appears that the effects of potential antioxidants are strongly dependent on the sources of oxidative damage. The same antioxidant may be protective under certain conditions and exert deleterious effects when the conditions are changed. Therefore a detailed understanding of the sources of the oxidative damage is required in order to design an adequate antioxidant mixture. 

Although significance of cholesterol hydroperoxides formation under physiological conditions is still unknown, they are apparently very important factors in the development of many pathophysiological disorders. Thus it has been shown [87] that 13ZE-Chl8 2-OOH exists in vivo in atherosclerotic lesions and is the primary toxin of oxidized human LDL. 

Thomas, J.P., Maiorino, M., Ursini, F. and Girotti, A.W. (1990) Protective action of phospholipid hydroperoxide glutathione peroxidase against membrane-damaging lipid peroxidation. In situ reduction of phospholipid and cholesterol hydroperoxides. J. Biol. Chem. 265 454-461. 

In 1963, cholesterol hydroperoxides were reported (36) in egg-containing foods irradiated by sunlight. Chicoye et al. (37) observed the following 5 photoxidation derivatives of cholesterol in spray-dried yolk exposed to either 40-watt fluorescent lamp (approx. 280 hours) or summer sunlight (5 hours) 33"hydroxy-cholest-5-en-7-one (7-keto) cholest-5-ene-33,7a-diol (7a-diol) cholest-5-ene-33,73-diol (73-diol) 5,63-epoxy-5a-cholestan-33-ol (3-epoxide) and 5a-cholestane-33, 5cx, 63-triol (triol). Subsequently, Tsai et al. (38) developed methodology to demonstrate the presence of 5,6a-epoxy-5a-cholestan-33-ol (a-epoxide) in dried egg products which were spiked with the epoxides. 

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