Antioxidant enzymes; possible mechanism of gold compound treatment in rheumatoid arthritis

Reactive oxygen species play a critical role in inflammatory processes including rheumatoid disorders. Antioxidant therapy strategies have been postulated for the treatment of rheumatoid diseases. In this study, we investigated activities and therapeutic implications of antioxidant enzymes in rheumatoid disorders. Activities of antioxidant enzymes glutathione peroxidase, glutathione reductase and catalase were examined in the blood of rheumatic patients and healthy controls. Activity of catalase was decreased significantly, while activities of glutathione peroxidase and glutathione reductase remained unchanged. Thioredoxin reductase is an antioxidant enzyme having an important regulatory task of thiol redox status and intracellular signaling processes coupled with the glutathione system. We also observed that in liver mitochondrial calf thioredoxin reductase was inhibited by antirheumatic drug goldthioglucose in the manner similar to intracellular thioredoxin reductase. Furthermore, during the treatment by goldthioglucose, gold is accumulated in lysosomes of macrophages. Our results suggest that although antioxidant enzyme activities were down-regulated in rheumatoid patients, we can decrease ROS generation by macrophages via inhibition thioredoxin reductase by goldthioglucose.