Radiation affects glutathione redox reaction by reduced glutathione peroxidase activity in human fibroblasts

Abstract

The glutathione (GSH) redox control is critical to maintain redox balance in the body’s internal environment, and its perturbation leads to a dramatic increase in reactive oxygen species (ROS) levels and oxidative stress which have negative impacts on human health. Although ionizing radiation increases mitochondrial ROS generation, the mechanisms underlying radiation-induced late ROS accumulation are not fully understood. Here we investigated the radiation effect on GSH redox reactions in normal human diploid lung fibroblasts TIG-3 and MRC-5. Superoxide anion probe MitoSOX-red staining and measurement of GSH peroxidase (GPx) activity revealed that high dose single-radiation (SR) exposure (10 Gy) increased mitochondrial ROS generation and overall oxidative stress in parallel with decrease in GSH peroxidase (GPx) activity, while GSH redox control was effective after exposure to moderate doses under standard serum conditions. We used different serum conditions to elucidate the role of serum on GSH redox reaction. Serum starvation, serum deprivation and DNA damage response (DDR) inhibitors-treatment reduced the GPx activity and increased mitochondrial ROS generation regardless of radiation exposure. Fractionated-radiation was used to evaluate the radiation effect on GSH reactions. Repeated fractionated-radiation induced prolonged oxidative stress by down-regulation of GPx activity. In conclusion, radiation affects GSH usage according to radiation dose, irradiation methods and serum concentration. Radiation affected the GPx activity to disrupt fibroblast redox homeostasis.

Mitochondrial Signaling Pathways Associated with DNA Damage Responses

“…A new radioprotective agent that targets mitochondria was recently investigated [ 142 ]. In irradiated normal human fibroblasts, IR has been shown to prevent GSH-mediated ROS scavenging by inactivation of GPx, resulting in damage to mitochondria, mitochondrial dysfunction, metabolic oxidative stress, and prolonged cell injury [ 22 ]. N-acetyl-5-methoxy-tryptamine (Melatonin) and MitoEbselen-2, a mitochondria-targeted GPx mimic, were used to stimulate GPx, which maintains mitochondrial-derived ROS levels.…”

“…The effect of radiation on redox control was studied in normal human fibroblasts. We recently discovered that IR increased ROS levels by inhibiting GPx’s ability to scavenge ROS [ 22 ]. As a result, the GSH redox potential is critical in maintaining redox homeostasis after radiation.…”

Boosting the therapy of glutamine-addiction glioblastoma by combining glutamine metabolism therapy with photo-enhanced chemodynamic therapy

“…27 To effectively kill tumor cells, the antioxidant GSH should be as low as possible and the reactive oxygen species (ROS) should be as many as possible, so that the excess ROS can oxidize large biomolecules (such as DNA, RNA, proteins, and lipids) and small biomolecules. 28,29 In addition to being produced within cells, ROS can also be generated by the transition metal ion (Fe 2+ , Mn 2+ , Cu + , etc. )-mediated Fenton reaction with H 2 O 2 in the microenvironment (e.g., Cu + + 3H 2 O 2 → Cu 2+ + HO − + • OH + 2H 2 O + O 2 ), which has been extensively used for tumor therapy (termed chemodynamic therapy, CDT).…”