The kinetics of Fe and Ca for the development of radiation-induced apoptosis by micro-PIXE imaging

Abstract To study the interactions between the induction of radiation-induced apoptosis and trace elements kinetics, human leukemia cells were irradiated in vitro by 60 Co γ rays, after which the cells were evaluated for the detection of apoptosis and trace element (Fe and Ca) imaging by micro-PIXE camera was carried out. In the early phase of apoptosis, high accumulation of Fe was observed in the cytosol. In the mid to end phase, the Fe accumulation was diminished; instead, Ca accumulated in the nucleus. The releasing of cytochrome-C agreed with the Fe accumulation. The caspase-3 and -8 activity agreed with the nuclear Ca accumulation in nucleus. There appear to be two steps for the development of apoptosis: (1) the signaling from cytosol to nucleus by cytochrome-C represented by Fe and (2) the degeneration of the nucleus by caspase represented by the nuclear Ca accumulation.