Reactive oxygen species damaged human serum albumin in patients with hepatocellular carcinoma

The role of reactive oxygen species (ROS) damaged human serum albumin (HSA) in hepatocellular carcinoma (HCC) has been investigated in the present study. HSA was modified by hydroxyl radical. Modification occurred in HSA was characterized by physico-chemical techniques. ROS modified HSA was found to be highly immunogenic in rabbits. The binding characteristics of circulating antibodies in HCC patients against native and ROS-modified HSA were assessed. HCC patients (n = 31) were examined by direct binding ELISA and their results were compared with healthy age-matched controls (n = 22). High degree of specific binding by 77.4% of HCC sera towards ROS-HSA, in comparison to its native analogue (p < 0.05) was observed. Competitive ELISA reiterates the direct binding results. Gel retardation assay further substantiated the enhanced recognition of ROS-HSA by circulating antibodies in HCC patients. The increase in total serum protein carbonyl levels in the HCC patients was largely due to an increase in oxidized albumin. Purified HSA of HCC patients (HCC-HSA) contained higher levels of carbonyls than HSA of normal subjects (normal-HSA) (p < 0.01). HCC-HSA was conformationally altered, with more exposure of its hydrophobic regions. Collectively, the oxidation of plasma proteins, especially HSA, might enhance oxidative stress in HCC patients.