Emerging Roles of Thioredoxin Cycle Enzymes in the Central Nervous System

The thioredoxins (Trxs) constitute a family of enzymes which catalyze the reduction of protein disulfide bonds. Recent animal studies have revealed the importance of the Trx superfamily in various experimental systems. For example, the homozygous disruption of the genes encoding cytoplasmic (TRX1) or mitochondrial Trx (TRX2) in mice generates lethal embryonic phenotypes. In contrast, transgenic mice overexpressing TRX1 show an extended life span and are relatively resistant to ischemia- mediated brain damage. In addition to their capacity to detoxify peroxides in concert with peroxiredoxins and Trx reductases, Trx isozymes perform multiple redox signaling functions mediated by their specific interaction with various proteins, including redox-regulated kinases and transcription factors. Recent studies indicate that specific isoforms of Trx cycle enzymes, targeted to different cell compartments, are key regulators of fundamental processes, such as gene expression, cell growth and apoptosis. The present review is primarily focused on the emerging neuroprotective role of these proteins in the central nervous system.