Preparation of an experimental mouse model lacking selenium-dependent glutathione peroxidase activities by feeding a selenium-deficient diet

Abstract

Relatively young (4 week old) selenium deficient (SeD) mice, which lack the activity of selenium dependent glutathione peroxidase (GSH Px) isomers, were prepared using torula yeast based SeD diet. Mice were fed the torula yeast based SeD diet and ultra pure water. Several different timings for starting the SeD diet were assessed. The weekly time course of liver comprehensive GSH Px activity after weaning was monitored. Protein expression levels of GPx1 and 4 in the liver were measured by Western blot analysis. Gene expression levels of GPx1, 2, 3, 4, and 7 in the liver were measured by quantitative real time PCR. Apoptotic activity of thymocytes after hydrogen peroxide (H 2 O 2) exposure was com pared. Thirty day survival rates after whole body X ray irradiation were estimated. Pre birth or right after birth starting of the SeD diet in dams was unable to lead to creation of SeD mice due to neonatal death. This suggests that Se is necessary for normal birth and healthy growing of mouse pups. Starting the mother on the SeD diet from 2 weeks after giving birth (SeD trial 2w group) resulted in a usable SeD mouse model. The liver GSH Px activity of the SeD trial 2w group was almost none from 4 week olds, but the mice survived for more than 63 weeks. Protein and gene expression of GPx1 was suppressed in the SeD trial 2w group, but that of GPx4 was not. The thymocytes of the SeD trial 2w group were sensitive to H 2 O 2 induced apoptosis. The SeD trial 2w group was sensitive to whole body X ray irradiation compared with control mice. The SeD trial 2w model may be a useful animal model for H 2 O 2 /hydroperoxide induced oxidative stress.

Effects of selenium deficiency on biological results of X-ray and carbon-ion beam irradiation in mice

“…The growth curve of SeD mice was similar to that of normal mice, which is consistent with previous findings. (14) The body weights of 10-week-old male and female SeD mice were 25.1 ± 1.73 and 22.2 ± 0.58 g (Supplemental Fig. 4B*), which were similar to or slightly higher than those of normal C3H/HeSlc mice at the same age (23.4 ± 1.3 g for males and 20.2 ± 1.1 g for females, as listed on the website of Japan SLC, Inc.).…”

“…SeD mice were prepared as previously described. (14) C3H/HeSlc mice on the 15th day of pregnancy were purchased from Japan SLC, Inc. (Shizuoka, Japan) and fed a normal diet (MB-1; Funabashi Farm Co., Chiba, Japan) and ultrapure water (Milli-Q water). Dams were fed the torula yeast-based SeD diet (F2SeDD; Oriental Yeast Co., Ltd., Tokyo, Japan) from 2 weeks after giving birth.…”

“…(13) Mice fed a Se-deficient (SeD) diet, SeD model mice, exhibit negligible Se-dependent GSH-Px activity in their tissues. (14) Based on the 30-day survival rate of SeD mice after whole-body X-ray irradiation, this mouse model shows radiation sensitivity. (14) Several indices have been utilized to estimate the biological effects of radiation on experimental animals.…”

“…(14) Based on the 30-day survival rate of SeD mice after whole-body X-ray irradiation, this mouse model shows radiation sensitivity. (14) Several indices have been utilized to estimate the biological effects of radiation on experimental animals. A conventional metric to estimate radiation effects on the whole body is the 30-day survival rate of a group of mice.…”

“…A conventional metric to estimate radiation effects on the whole body is the 30-day survival rate of a group of mice. (14)(15)(16) A survival rate estimates the ratio of biologically significant events that occur in a group of subjects, but not the degree of radiation-induced damage in an individual animal. Leg contracture is used as a quantitative index of radiation effects vs an identical body.…”