Plasma protein hydroperoxides during aging in humans: correlation with paraoxonase 1 (PON1) arylesterase activity and plasma total thiols.

BACKGROUND AND AIMS: Oxidative stress is thought to play a major role in the development of several age-dependent diseases. Proteins are major targets for oxidative attack. Protein hydroperoxides are formed by hydroxyl and singlet oxygen attack on protein, forming relatively stable hydroperoxides on histidine, tyrosine and tryptophan residues. This study investigated the levels of plasma protein hydroperoxides and antioxidant potential of plasma during aging in humans. We correlated the protein hydroperoxide formation with plasma antioxidant potential, paraoxonase 1 (PON1) arylesterase activity and plasma total thiols. METHODS: The protein hydroperoxides and antioxidant potential were measured in plasma of human subjects aged between 20 and 81 years of both genders. RESULTS: Increase in plasma protein hydroperoxides and decrease in plasma antioxidant potential were observed as function of human age. CONCLUSION: This study provides strong correlation between plasma protein hydroperoxides formation and decrease in plasma antioxidant potential during aging. PON1 arylesterase activity and plasma total thiols levels were also found to show significant correlation with increasing levels of plasma protein hydroperoxides during aging. The plasma protein hydroperoxides provide a reliable marker of long-term redox balance and degree of oxidative stress during aging process.