Expressions of IRE1α and XBP1 mRNA and proteins in mouse testis cells induced by low dose ionizing radiation

Objective: To detect the expressions of inositol-requiring enzyme-1α (IRE1α) and X box-binding protein-1 (XBP1) mRNA and proteins in mouse testis cells, and to explore the role of IRE1-XBP1 pathway activation in the endoplasmic reticulum stress induced by low dose radiation (LDR) in the mouse testis cells. Methods: A total of 50 healthy male ICR mice were randomly divided into 10 groups. After the mice were irradiated with 75 mGy X-ray in whole body at different time (0, 3, 6, 12, and 24 h) or with different doses (0, 50, 75, 100, and 200 mGy) of X-ray for 12 h, the expression levels of IRE1α, T-XBP1 and S-XBP1 mRNA and proteins were measured by real-time quantitative PCR and Western blotting method, respectively. Results: The expression levels of IRE1α, T-XBP1 and S-XBP1 mRNA (except T-XBP1 and S-XBP1 mRNA at 3 h after irradiation) in the testis cells of the mice after irradiated with 75 mGy X-ray for 0-24 h were increased with the time prolongation, and reached to the maximum value at 6 h after irradiation, then were gradually decreased. Compared with 0 h group, the expression levels of IRE1α mRNA (6, 12, and 24 h after irradiation), T-XBP1 mRNA and S-XBP1 mRNA (6 and 12 h after irradiation) were significantly increased (P < 0.05 or P < 0.01); the expression intensities of IRE1α and S-XBP1 proteins were increased; the expression intensities of IRE1α (6 and 12 h after irradiation) and S-XBP1 (24 h after irradiation) proteins were increased most significantly, but the expression intensity of T-XBP1 protein was slightly decreased. The expression levels of IRE1α, T-XBP1 and S-XBP1 mRNA in the testis cells of the mice after irradiated with 0-200 mGy for 12 h were increased, and reached to the maximum values after 75 mGy irradiation, then they were gradually decreased, even below 0 mGy. Compared with 0 mGy group, the expression levels of IRE1α mRNA in the testis cells of the mice in 75 and 200 mGy groups and the expression levels of T-XBP1 mRNA and S-XBP1 mRNA in 75 mGy group were significantly increased (P < 0.05 or P < 0.01); the expression intensities of IRE1α protein in 75 mGy group and S-XBP1 protein in 75 and 200 mGy groups were increased mostly, while the expression intensity of T-XBP1 protein had no obvious change. Conclusion: LDR can induce the increase of IRE1α and S-XBP1 mRNAs and proteins, and activate the IRE1-XBP1 pathway in endoplasmic reticulum stress. (authors)