Which Antioxidant System Shapes Intracellular H2O2 Gradients?

Cellular antioxidant systems control the levels of hydrogen peroxide (H 2 O 2 ) within cells. Multiple theoretical models exist that predict the diffusion properties of H 2 O 2 depending on the rate of H 2 O 2 generation and amount and reaction rates of antioxidant machinery components. Despite these theoretical predictions, it has remained unknown how antioxidant systems shape intracellular H 2 O 2 gradients. The relative role of thioredoxin (Trx) and glutathione systems in H 2 O 2 pattern formation and maintenance is another disputed question. Here, we visualized cellular antioxidant activity and H 2 O 2 gradients formation by exploiting chemogenetic approaches to generate compartmentalized intracellular H 2 O 2 and using the H 2 O 2 biosensor HyPer to analyze the resulting H 2 O 2 distribution in specific subcellular compartments. Using human HeLa cells as a model system, we propose that the Trx system, but not the glutathione system, regulates intracellular H 2 O 2 gradients. Antioxid. Redox Signal. 31, 664-670.