Radiation Protection by Cysteamine against the Lethal Effects of Intracellularly Localized Auger Electron, a- and ß-Particle Emitting Radionuclides

Abstract

The mechanisms by which DNA-incorporated radionuclides impart lethal damage to mammalian cells were investigated by examining the capacity of cysteamine (MEA) to protect against lethal damage to V79 cells caused by unbound tritium (3H2O), DNA-incorporated 131/125I-iododeoxyuridine (IdU) and the alpha-particle emitter 210Po-citrate. Radiolabeled cells were maintained at 10.5 degrees C for 72 h in the absence or presence of MEA (0.65-2.6 mM) and the surviving fraction was determined. Protection against lethal damage caused by 3H2O, 131IdU or 125IdU and 210Po-citrate depended on the concentration of MEA with maximum protection at 1.3-1.9 mM. The dose modification factors obtained at 1.3 mM for the radiochemicals were 2.5 +/- 0.3, 1.8 +/- 0.2, 1.7 +/- 0.1 and 1.4 +/- 0.1, respectively. MEA provides more protection against indirect than direct effects of ionizing radiation, and indirect effects play a role in the radiotoxicity of Auger electron emitters incorporated into the DNA of mammalian cells.

Nuclear data for the cyclotron production of 117 Sb and 90 Nb

“…Auger electron emitting radionuclides have potential for the therapy of small-size cancers because of their high level of cytotoxicity, low-energy, high linear energy transfer, and short range biologic effectiveness [2][3][4][5][6][7]. Besides the direct effect of Auger electrons on DNA double strands, an indirect radiation effect of Auger energy deposition will occur via production of radicals.…”

“…Besides the direct effect of Auger electrons on DNA double strands, an indirect radiation effect of Auger energy deposition will occur via production of radicals. The radicals diffuse freely in the intracellular space and can cause further DNA damage [4][5][6][7]. 64 Cu combines both β + and Auger electron emissions in its decay mode, hence considered as promising radionuclide targeting DNA.…”