Keywords: apoptosis, reactive oxygen species, ROS, eugenol, mouse thymocytes, mitochondrial membrane potential, gamma irradiation, low radiation, cellular oxidative damage, cellular radiosensitivity
The involvement of cellular oxidative damage in the apoptotic death induced in γ-irradiated mouse thymocytes
Radiation-induced cellular oxidative damage and the consequent apoptotic death were investigated in mouse thymocytes in the presence or absence of eugenol to understand the mechanism of modification in cellular radiosensitivity. The results showed the radiation-induced generation of intracellular Reactive Oxygen Species (ROS) in γ-irradiated thymocytes, which were detected within a low to moderate dose range of radiation exposure (sub cGy to 2 Gy) using 2′,7′-dichlorodihydrofluorescein diacetate (DCH-FDA) as a fluorescent probe. However, the dose response of the ROS generation was found to be different at low and high doses/rates, which was significantly inhibited when the cells were treated with eugenol. There was a decrease in the mitochondrial membrane potential (ΔΨmt) after the irradiation of cells, which was prevented when cells were pretreated with eugenol. The population of thymocytes with a reduced nuclear diameter was found to progressively increase with the post-irradiation incubation time following exposure to a dose of 5 Gy, which was, however, prevented in the thymocytes that were treated with eugenol. These results followed a pattern that is similar to the annexin-V method that was further verified in control and irradiated samples. We have found a correlation in cellular oxidative stress, a decrease in ΔΨmt and the induction of apoptotic cell death, suggesting the involvement of oxidative damage and alterations in the mitochondria in radiation-induced apoptosis in thymocytes.