Thioredoxin - a magic bullet or a double-edged sword for mammalian aging?

After the discovery of thioredoxin as a reductant for many important enzymes in the early 1960s, biological roles of thioredoxin in pathophysiology have been examined using various species and experimental models, e.g., yeast, invertebrates, rodents, and humans. A large number of studies demonstrated that thioredoxin plays an essential role to maintain a reduced cellular environment and possesses many beneficial effects by maintaining cellular/organ functions and against diseases. However, an important question that remains to be answered is whether thioredoxin could attenuate aging by reducing oxidative damage and changing cellular redox state, which alters redox-sensitive signaling pathways. To address this important question, we have been conducting aging studies with transgenic and knockout mice, and transgenic rats to examine whether the upregulation or downregulation of thioredoxin alters lifespan and age-related pathology. Aging studies conducted by our laboratory and others revealed that the roles of thioredoxin on pathophysiology seem to be more complex than our initial expectations as a potential magic bullet to solve the issues with age. Recent studies indicate that thioredoxin could have both beneficial and potentially deleterious effects on aging and age-related diseases. To critically evaluate the biological effects of thioredoxin on aging and age-related diseases, studies require further consideration to assess additional factors, e.g. levels of thioredoxin in different cellular compartments, different effects in each cell/tissue/organ, physiological aging vs. pathology, and/or at different life stages.