The Effect of Cysteamine on the Radiation-Induced Apoptosis / 대한방사선종양학회지

ABSTRACT

PURPOSE: To investigate the pathways of radiation induced apoptosis and the effect of cysteamine (beta-mercaptoethylamine), as a radioprotector, on it. MATERIALS AND METHODS: HL-60 cells were assigned to control, irradiated, and cysteamine (1 mM, 10mM) pretreated groups, Irradiation was given in a single fraction of 10 Gy (6 MV x-ray) and cysteamine was administered 1 hour before irradiation. The activities of caspase-8 were measured in control and irradiated group to evaluate its relation to the radiation induced apoptosis. To evaluate the role of cysteamine in radiation induced apoptosis, the number of viable cells, the expression and activity of caspase-3, and the expression of poly (ADP-ribose) polymerase (PARP) were measured and compared after irradiation the HL-60 cells with cysteamine pretreatment or not. RESULTS: The intracellular caspase-8 activity, known to be related to the death receptor induced apoptosis, was not affected by irradiation (p>0.05). The number of viable cells began to decrease from 6 hours after irradiation (p>0.05), but the number of viable cells in 1 mM cysteamine pretreated group was not decreased afger irradiation and was similar to those in the control group. In caspase-3 analyses, known as apoptosis executioner, its expression was not different but its activity was increased by irradiation (p>0.05). However, this increase of activity was suppressed by the pretreatment of 1mM crysteamine. The cleavage of PARP, thought to be resulted from caspase-3 activation, occurred after irradiation, which was attenuated by the pretreatment of 1mM cysteamine. CONCLUSION: these results show that radiation induced apoptotic process is somewhat different from death receptor induced one and the pretreatment of 1 mM cysteamine has a tendency to decrease the radiation-induced apoptosis in HL-60 cells.