Effects of different doses of ionizing radiation on expression of TLR4 and related cytokines in J774A. 1 cell line

Objective: To observe the changes in the secretion of IL-12, IL-18 and the expressions of TLR4 in J774A. 1 cells after ionizing irradiation, and explore the mechanism of Toll signaling pathway. Methods: J774A.1 cells were divided into low dose (0.075 Gy) and high dose (2.00 Gy) irradiation groups, each group included sham irradiation, 4, 8, 16, 24, 48 h after irradiation subgroups. Flow cytometry and ELISA were used to detect the expression of TLR4 and the protein levels of IL-12 and IL-18, respectively. Results: At early stage, both of IL-12 (4 h)and IL-18 (4 h) expressed more than sham irradiation after low dose ionizing radiation, and then gradually returned to the level in sham irradiation group. After high dose ionizing radiation, the expression of IL-12 kept higher level compared with sham irradiation group at 4-24 h (P<0.05 or P<0.01), and then returned to the normal level at 48 h; while the expression of IL-18 was similar with that in low dose irradiation group, it was up-regulated at 4 h after irradiation (P<0.05), and then gradually returned to the control level. Conclusion: Ionizing radiation can increase the expression of TLR4 and the protein levels of IL-12, IL-18 and promote the immune response and start innate immunity. (authors)