The oxido-redox potential of albumin Methodological approach and relevance to human diseases

In humans, an increased synthesis of reactive oxygen species (ROS) maybe a relevant cause of amplification of physiologic processes resulting in inflammatory organ damage or neoplasia. Efficient anti-oxidative systems targeting oxidative stress are thus essential to prevent tissue damage. In plasma, proteins proved to be the first line of defence against ROS and albumin, the highest concentration plasma protein, has a key role in this antioxidant function. Recent studies have clearly documented that albumin oxido-redox potential changes upon oxidation by different oxidants thus becoming a deputy biomarker of this process. ROS react primarily with the free (34)CySteine ((34)Cys) residue of albumin to form two reversible intermediate derivatives, sulfenic-(SOH-alb) and sulfinic acid (SO2H-alb), resulting in sulfonic acid (SO3H-alb), the final stable product of the reaction. Upon stable oxidation (SO3H-alb), albumin properties are altered: the protein becomes more susceptible to trypsin digestion and is degraded faster compared to the non-oxidized counterpart. The present review focuses on the characterization of albumin chemical changes induced by ROS, their relevance in human pathology and the most recent advances in the approach to oxidation adduct analysis. (C) 2009 Elsevier B.V. All rights reserved.