Abstract: 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 heatly 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 for12 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.

Key words: low dose radiation, testis, endoplasmic reticulum stress, inositol-requiring enzyme 1α, X-box binding protein 1