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

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Vol. 189; no. 1; pp. 437 - 442
• Main Authors: Harada, S., Tamakawa, Y., Ishii, K., Tanaka, A., Satoh, T., Matsuyama, S., Yamazaki, H., Kamiya, T., Sakai, T., Arakawa, K., Saitoh, M., Oikawa, S., Sera, K.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2002
• Subjects: Apoptosis; Calcium; Cells; Cobalt; Enzymes; Iron; Irradiation; Medical imaging; Micro-PIXE camera; Proton beams; Radiation; Reaction kinetics; Trace elements; Micro-PIXE camera; 82.80.Ej; Zn; Radiation; 87.50.Gi; Ca; Apoptosis; Fe
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/S0168-583X(01)01121-1

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, Ca, Zn) imaging was carried out. The frequency of apoptosis, i.e. the number of apoptotic bodies per 100 nuclei, was obtained by microscopic assay using TUNEL staining at 400× magnification. The trace element distribution in the cell was determined by micro-PIXE using 2 MeV proton beams. In the early phase of apoptosis, the maximum level of Fe accumulation was observed in the cell stroma. In the mid to end phase, Fe accumulation was diminished, and instead, Ca accumulation increased and Zn decreased in the nucleus. There appear to be two steps for the development of apoptosis: (1) the signaling from cell stroma to nucleus by Fe or an Fe-containing enzyme; and (2) the degeneration of the nucleus by Ca-dependent enzyme, and release of Zn from digested nucleus. Those strong accumulations may be new markers for apoptosis.