Reactive oxygen species mediated membrane damage induced by fullerene derivatives and its possible biological implications.

Fullerenes have attracted considerable attention in recent years due to their unique chemical structure and potential applications. Hence it is of interest to study their biological effects. Using rat liver microsomes as model systems we have examined the ability of the most commonly used fullerene, C60 and its water-soluble derivative, C60(OH)18 to induce membrane damage on photosensitization. For photoexcitation, UV or tungsten lamps were used. Damage was assessed as lipid peroxidation products like conjugated dienes, lipid hydroperoxides and thiobarbituric acid reactive substances (TBARS). protein oxidation in the form of protein carbonyls, besides loss of membrane bound enzymes. Both fullerene derivatives induced significant oxidative damage. The alterations induced were both time- and concentration-dependent. Role of different reactive oxygen species (ROS) in the damage induced was examined by various scavengers of ROS and by deuteration of the buffer. The changes induced by C60 were predominantly due to 1O2 while that by C60(OH)18 was mainly due to radical species. Biological antioxidants such as glutathione, ascorbic acid and alpha-tocopherol were capable of inhibiting membrane damage induced by both the fullerenes. However, the damage induced by C60(OH)18 was more for both lipids and proteins than that showed by C60. C60 also showed enhancement in the formation of lipid peroxidation in sarcoma 180 ascites microsomes. In conclusion, our studies indicate that fullerene/its derivative can generate ROS on photoexcitation and can induce significant lipid peroxidation/protein oxidation in membranes and these phenomena can be prevented by endogenous/natural antioxidants.