The thioredoxin system is a crucial antioxidant defense mechanism in cells, comprising thioredoxin, thioredoxin reductase, and NADPH, which together maintain the redox balance by reducing disulfide bonds in proteins. This system plays a significant role in cellular processes like DNA synthesis, repair, and regulation of apoptosis, making it a potential target for therapeutic interventions in diseases such as cancer and neurodegenerative disorders.