title: Spatio-temporal changes in glutathione and thioredoxin redox couples during ionizing radiation-induced oxidative stress regulate tumor radio-resistance.
abstract: Ionizing radiation (IR)-induced oxidative stress in tumor cells is effectively managed by constitutive and inducible antioxidant defense systems. This study was initiated to understand the relative contribution of different redox regulatory systems in determining the tumor radio-resistance. In this study, human T-cell lymphoma (Jurkat) cells were exposed to IR (4 Gy) and monitored for the spatio-temporal changes in cellular redox regulatory parameters. We monitored the changes in the levels of reactive oxygen species (ROS) (total, mitochondrial, primary, and secondary), thiols (total, surface, and intracellular), GSH/GSSG ratio, antioxidant enzyme activity viz. thioredoxin (Trx), Trx reductase (TrxR), glutathione peroxidase, and glutathione reductase with respect to time. We have also measured protein glutathionylation. We observed that tumor cells mount a biphasic response after IR exposure which can be divided into early (0-6 h) and late (16-48 h) responses in terms of changes in cellular redox parameters. During early response, constitutively active GSH and Trx systems respond to restore cellular redox balance to pre-exposure levels and help in activation of redox-sensitive transcription factor Nrf-2. During late response, increase in the levels of antioxidants GSH and Trx rescue cells against IR-mediated damage. We observed that disruption of either glutathione or thioredoxin metabolism led to partial impairment of ability of cells to survive against IR-induced damage. But simultaneous disruption of both the pathways significantly increased radio sensitivity of Jurkat cells. This highlighted the importance of these two antioxidant pathways in regulating redox homeostasis under conditions of IR-induced oxidative stress.
authors.affiliation: a Radiation Biology and Health Sciences Division, Modular Laboratories, Bhabha Atomic Research Centre , Trombay, Mumbai , India.
authors.forename: R S
authors.initials: RS
authors.lastname: Patwardhan
authors.forename: D
authors.initials: D
authors.lastname: Sharma
authors.forename: R
authors.initials: R
authors.lastname: Checker
authors.forename: M
authors.initials: M
authors.lastname: Thoh
authors.forename: S K
authors.initials: SK
authors.lastname: Sandur
mesh_terms: D021581:Active Transport, Cell Nucleus; D017209:Apoptosis / Q000528:radiation effects; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000528:radiation effects; D005720:Gamma Rays / Q000009:adverse effects*; D005978:Glutathione / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006706:Homeostasis; D006801:Humans; D019169:Jurkat Cells / Q000528:radiation effects; D007963:Leukocytes, Mononuclear / Q000378:metabolism / Q000528:radiation effects; D008928:Mitochondria / Q000378:metabolism / Q000528:radiation effects; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000502:physiology; D051267:NF-E2-Related Factor 2 / Q000502:physiology; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D011836:Radiation Tolerance; D017382:Reactive Oxygen Species / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013879:Thioredoxins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection
chemical_list: D004273:DNA, Neoplasm; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D013438:Sulfhydryl Compounds; D013879:Thioredoxins; D019255:NADPH Oxidases; D005978:Glutathione
keywords: antioxidant; ionizing radiation; oxidative stress; radio-sensitivity; redox homeostasis