The role of small GTPases in ionizing radiation damage in rat model

Objective: Acute and late effects of ionizing radiation on living organisms are mainly known as the generation of reactive oxygen species (ROS), apoptosis and DNA damage. The small GTPases, which are Rac1, RhoA, and Cdc42, are involved in intracellular ROS formation and apoptosis mechanisms. In this study, it was aimed to investigate the role of small GTPases involved in radiation-induced damage to testes and bone marrow tissues. Methods: Whole body irradiation was applied to the rats at 3 different doses (0.02 Gy; 0.1 Gy; 5 Gy) except the control group. Testicular and bone marrow tissues were removed at 2 hours, 24 hours and 7 days after radiation exposure. Testicular and bone marrow tissue damage was analyzed by histological methods and Rac1 and RhoA expressions by immunohistochemical (IHC) staining. Apoptosis was assessed by IHC staining of active caspase-3 expression. In order to evaluate ROS in testicular tissue, intracellular ROS, superoxide dismutase (SOD) and malondialdehyde (MDA) analyses were performed using biochemical methods. Rac1 and RhoA activation were analyzed by biochemical methods. Results: Testicular tissue damage and increased apoptosis were detected in all irradiated groups, depending on time and dose. Depending on the dose and time in the all radiation groups, Rac1 expressions decreased compared to the control group and RhoA expressions increased. In addition, it was found that intracellular ROS and MDA levels increased and SOD levels decreased in the all radiation groups compared to the control group. Conclusion: It has been suggested that small GTPases may have a role in radiation-induced testicular damage. It has been suggested that Rac1 and RhoA may have some of the effect of increasing testicular damage by increasing intracellular ROS generation and lipid peroxidation. Key Words: Apoptosis, Ionizing radiation, Small GTPase, NADPH oxidase, Reactive oxygen species (ROS), Radiation damage