Title: Radiation-induced apoptosis in SCID mouse spleen after low dose or low dose-rate irradiation

Authors: A. Takahashi, K. Ohnishi, T. Ohnishi

Addresses: Department of Biology, Nara Medical University, Kashihara, Nara 634-8521, Japan. ' Department of Biology, Nara Medical University, Kashihara, Nara 634-8521, Japan. ' Department of Biology, Nara Medical University, Kashihara, Nara 634-8521, Japan

Abstract: Concerning human health, studies of radioadaptive responses are quite important in radiation biology, because the radiation response may strongly depend on previous radiation exposure. Therefore, we have studied the radiation-induced Bax and apoptosis in mouse spleen after whole-body irradiation with low dose or low dose-rate. By use of severe combined immunodeficiency (SCID) mouse defective DNA-PK activity, we examined the role of DNA-PK activity in radioadaptation induced by pre-irradiation with low dose or low dose-rate. Based on immunohistochemical analyses in the present study, we detected the dose- and time course-dependent induction of Bax and apoptosis after acute irradiation especially in splenic white pulp of both SCID and the parental mice. They were significantly suppressed in the parental mice 2 weeks after low-dose (0.45 Gy) irradiation or immediately after low dose-rate (0.001 Gy/min for 25 h, 1.5 Gy) irradiation, but not SCID mice under each condition. These data suggest that DNA-PKcs (expressed in the parental mice, not SCID mice) might play a major role on the suppression of the acute radiation-induced apoptosis in spleen by low dose or low dose-rate irradiation. We expect that the present findings will provide useful information for the clarification of radioadaptive response.

Keywords: DNA-PK; adaptive response; low dose-rate; Bax; apoptosis; spleen; low radiation.

DOI: 10.1504/IJLR.2004.003871

International Journal of Low Radiation, 2004 Vol.1 No.2, pp.199 - 207

Published online: 10 May 2004 *

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