Spatio-temporal changes in glutathione and thioredoxin redox couples during ionizing radiation-induced oxidative stress regulate tumor radio-resistance

• Published in: Free radical research Vol. 49; no. 10; pp. 1218 - 1232
• Main Authors: Patwardhan, R. S., Sharma, D., Checker, R., Thoh, M., Sandur, S. K.
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 03.10.2015
• Subjects: Active Transport, Cell Nucleus; antioxidant; Apoptosis - radiation effects; DNA Damage; DNA, Neoplasm - radiation effects; Gamma Rays - adverse effects; Glutathione - antagonists & inhibitors; Glutathione - metabolism; Homeostasis; Humans; ionizing radiation; Jurkat Cells - radiation effects; Leukocytes, Mononuclear - metabolism; Leukocytes, Mononuclear - radiation effects; Mitochondria - metabolism; Mitochondria - radiation effects; NADPH Oxidases - antagonists & inhibitors; NADPH Oxidases - physiology; Neoplasm Proteins - antagonists & inhibitors; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; NF-E2-Related Factor 2 - physiology; Oxidation-Reduction; Oxidative Stress; Radiation Tolerance; radio-sensitivity; Reactive Oxygen Species - metabolism; redox homeostasis; RNA Interference; RNA, Small Interfering - genetics; Sulfhydryl Compounds - metabolism; Thioredoxins - antagonists & inhibitors; Thioredoxins - genetics; Thioredoxins - metabolism; Time Factors; Transfection; radio-sensitivity; antioxidant; redox homeostasis; ionizing radiation; oxidative stress
• ISSN: 1071-5762; 1029-2470
• DOI: 10.3109/10715762.2015.1056180

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.