Inhibition of oxidative modification of proteins by RU486

Objectives: To elucidate further the antioxidant properties of RU486. We determined whether it can protect biologic molecules such as proteins (albumin, low-density lipoprotein [LDL] and oxidized LDL) from damage by pre- existing lipid peroxides. Design: In vitro study. Interventions: We tested the effects of RU486 on the formation of fluorescent oxidatively modified proteins by pre-existing lipid peroxides. We used two model systems, the incubation of oxidized linoleic acid with serum albumin and the incubation of human LDL with copper. Main Outcome Measures: The formation of modified protein was established by determining fluorescence at excitation wavelength of 330 nm and emission wavelength between 390 and 500 nm. Modified protein has a characteristic emission between 425 and 430 nm. Results: The addition of increasing amounts of RU486 inhibited the formation of fluorescent oxidatively modified protein products in both model systems. Conclusion: These results provide evidence that RU486 not only can prevent the formation of lipid peroxide, but also can block the formation of fluorescent protein adducts in the presence of pre-existing lipid peroxides.