Gene expression profiles in mouse liver after long-term low-dose-rate irradiation

Abstract

In order to assess the biological effects of low dose radiation, transcriptional changes induced by long-term low-dose-rate gamma irradiation were analyzed by DNA microarray. The exposure experiments were repeated twice at similar dose-rates. Three groups of 8 weeks old male C57BL/6J mice were exposed to whole body irradiation at dose-rates of either 32 nGy/min, 650 nGy/min or 12500 nGy/min for 485 days, and secondly at 38 nGy/min, 767 nGy/min or 15300 nGy/min for 401 days. Another group was sham irradiated as a control. The expression levels of 6 irradiated animals were individually compared with that of pooled control animals. The data showed a relatively large variation in expression levels among 6 individuals and the number of genes showing common changes was limited: 25 and 15 genes were judged to show more than 1.5-fold modulation at 12500 or 15300 nGy/min and 650 or 767 nGy/min, respectively, and surprisingly 2 genes showed more than 2-fold modulation even at the lowest dose rate of 32 or 38 nGy/min. Our results indicate that there are a few genes responding to the very low-dose-rate irradiation. Moreover, the functional analysis suggests the biological function of lipid metabolism and the disease of obesity are most significant to the genes showing modulation at 12500 or 15300 nGy/min.