Programmed Cell Death in Whole Body and Organ Systems by Low Dose Radiation

Abstract

Programmed cell death /Whole body /Organ culture /Low dose radiation /Mouse New whole-body and organ systems were established to detect interphase cell death in the thymus, spleen and epithelial cells of intestinal crypts by low-dose radiation. Frozen sections of the thymus, spleen and intestine as thick as 8,um were made after X-irradiation of whole body or removed organs, and then sections were stained with 0.02% erythrosin B solution. In unirradiated controls, a few numbers of erythrosin B positive cells (dead or dying cells) were observed in the thymus, spleen and intestinal crypt as a single cell death. When X rays were given to various strains of mice as a whole body dose, clusters of erythrosin B positive cells were produced. They appear at 2 hr after irradiation and reached maximum at 4 hr, remaining at a similar level until 8 hr after irradiation. The number of erythrosin B positive cells decreased after then by the elimination of dead cells, and they were observed like a single cell death at 24 hr after irradiation. When erythrosin B positive cells were scored 4 hr after irradiation, their total number and the number of cluster increased with increasing doses of X rays in the dose range from 0.05 to 0.5 Gy. It is noted that there were large differences in the radiation susceptibility among the inbred strains of mice for the induction of interphase cell death of thymic lymphocytes: e.g., high susceptibility in C57BL/6J and AKR/J, intermediate in N4, A/J, PT and ST, low in C3H/HeJ, HT, 101/H and DBA/2J, indicating that interphase cell death is genetically programmed.Similar results were observed with some chemical mutagens. Although a large increase of erythrosin B positive cells was observed in the thymus and spleen with methylprednisolone, there was no increase in the intestinal crypt, and vice versa with bleomycin, suggesting the organ specificity for the induction of interphase cell death by chemicals.For the in vitro method, the removed thymus was irradiated on the agar plate, and then incubated on the agar plate which was placed on the grid in the medium, so that the medium comes up to the organ through the agar plate. Frozen sections were made and stained with erythrosin B solution in the same way as the in vivo method. The number of erythrosin B positive cells in the organ culture system reached maximum at 5 hr after X-irradiation, e.g. slightly later than in the whole-body system. The efficiency was about 60% in C57BL/6J mice when compared with whole-body system.

Inflammatory-type responses after exposure to ionizing radiation in vivo: a mechanism for radiation-induced bystander effects?

“…Since we have shown that induction of macrophage activities is correlated with radiation-induced apoptosis, and it is known that the level of apoptosis after radiation exposure varies between di erent mouse strains (Nomura et al, 1992), one possible explanation for these results would be that there are higher levels of apoptosis in C57BL/6 mice than in CBA/Ca mice, leading to higher enzyme activities in the former. To investigate this possibility, we counted apoptotic cells at various times after irradiation in the spleens of duplicate animals.…”

“…To investigate the relationship between cell death and macrophage activation we turned to the DBA/2 strain, which is known to be particularly resistant to radiation-induced apoptosis (Nomura et al, 1992). Spectrophotometric measurements in spleen lysates from these mice 24 h after 4 Gy irradiation showed that the levels of acid b-galactosidase were approximately twofold higher than the corresponding CBA/Ca level.…”

PTEN status switches cell fate between premature senescence and apoptosis in glioma exposed to ionizing radiation

“…35,36 It has been known that apoptosis is readily induced in tumors derived from hematopoietic, lymphoid, and germ cells, but some solid tumors derived from epithelial cells show resistance to apoptosis after IR exposure. 37,38 Recent evidence has shown that IR prematurely induces senescent phenotypes, instead of apoptosis, before the Hayflick limit, which is known as stressinduced premature senescence. We also previously reported that IR induces premature senescence in breast, colon, and lung carcinoma, and in tumor tissue of xenografted mice.…”

Differential post-translational modification of the tumour suppressor proteins Rb and p53 modulate the rates of radiation-induced apoptosis in vivo

“…In order to begin to de®ne key molecular events that control the rate of apoptosis in vivo, a quantitative analysis of the extent of apoptosis was performed in splenic tissue from two inbred strains of mice with a dierent genetic predisposition to radiation damage (Nomura et al, 1992;Roderick, 1963;Watson et al, 1997). The majority of studies on the sensitivity of cells to ionizing radiation in vivo have employed doses sucient to elicit animal death (5 ± 10 Gy) (Komarova et al, 2000;Merritt et al, 1994;Midgley et al, 1995;Wilson et al, 1998).…”

“…In addition, as the majority of tumour cells in culture have mutations or deletions in the tumour suppressor proteins that play a role in cell cycle progression including p16, p53 and Rb, cultured cells do not necessarily provide the best model for studying the genetic factors that determine sensitivity to radiation in vivo. Here we report on the use of inbred strains of mice with a known dierential sensitivity to radiation damage (Nomura et al, 1992;Roderick, 1963;Watson et al, 1997) to determine whether rates of apoptosis can be aected by dierential modulation of the p53-p21/Rb axis in non-transformed cells. Using the spleen as a model we show dramatic dierences in the susceptibility of these animals to radiation induced apoptosis dependent on their genetic background.…”