Barbara Szolc-Kowalska, Presenter: Nothing to Disclose

Kaori Nakamura, Abstract Co-Author: Nothing to Disclose

Benjamin Haley, Abstract Co-Author: Nothing to Disclose

Tatjana Paunesku PhD, Abstract Co-Author: Nothing to Disclose

Tetsuya Ono, Abstract Co-Author: Nothing to Disclose

Gayle E. Woloschak PhD, Abstract Co-Author: Nothing to Disclose

Akiko Hagiwara, Abstract Co-Author: Nothing to Disclose

We are investigating effects of irradiation on a radiosensitive mouse mutant model_the wasted mouse (wst). The wasted mouse shows a triad of symptoms: i) motor neuron disease that results in death of the affected animals by the 28-30 days of age; ii) immunodeficiency in certain T-cell subpopulations, and iii) radiosensitivity. In previous experiments we found in wasted mice a several fold decrease in the quantity of the protein proliferating cell nuclear antigen (PCNA) in most of the tissues tested (liver, kidney, heart, brain and spinal cord) and particularly in organs of the immune system_thymus and spleen (red and white pulp both). This pattern of expression is not found in young animals (postnatal day 12) but in mice 22 days or older. We also found increased levels of early apoptotic, Annexin V positive cells in irradiated healthy control animals, whereas wasted mice (wst/wst) showed a high basal level of apoptosis which did not change significantly in response to irradiation. In this study we further investigated effects of radiation treatment on expression of PCNA, accumulation of gamma-H2AX and late apoptosis in cells stained using five different fluorophores.Exposure of cells to radiation causes damage of cellular DNA, particularly formation of DNA double-strand breaks (DSBs) and induces formation of gamma-H2AX nuclear foci. We investigated radiation effects in both dose and time dependent manner.

Two groups of animals (wasted and control mice) were sacrificed 3 and 24 hours after receiving 1 or 2 Gy dose of gamma-ray irradiation. Thymus, spleen and bone marrow were harvested and homogenized into a single cell suspension. Collected cells were fixed, stained with fluorescent dyes or fluorescently labeled antibodies (violet dead-live cell stain, anti-PCNA, anti-gamma H2AX, anti-BrDU antibodies and 7-AAD) and analyzed by flow cytometry.

PCNA expression pattern confirmed our previous results showing similar PCNA levels in wasted non-irradiated mice and the irradiated healthy mice. Late apoptosis results were similar to the results obtained for early apoptosis showing no significant difference for wasted mice and increase of late and early apoptotic cells in healthy mice after radiation treatment. Basal level of gamma-H2AX staining in wasted mice was increased compared to normal mice and showed further increase in response to higher doses of radiation treatment.

While irradiated healthy mice show similar extent of apoptosis and level of PCNA expression as wasted mice, total numbers of DNA double-strand breaks in irradiated wasted mice are much higher than in healthy mice irradiated with the same gamma-ray doses. This is a result of the higher initial number of gamma H2AX positive foci in wasted mouse lymphocytes.

Szolc-Kowalska, B, Nakamura, K, Haley, B, Paunesku, T, Ono, T, Woloschak, G, Hagiwara, A, Radiation Effects on Lymphocytes of Radiosensitive Wasted Mouse: Induction of H2ax Phosphorylation, Apoptosis, and Pcna Expression.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/6001446.html