Background: In clinical radiotherapy, in addition to the symptoms of radiation damage in the irradiated area, normal tissues can produce damage other than direct irradiation due to bystander effects. We often use dexamethasone to relieve symptoms, thereby protecting the surrounding normal tissues, and may also protect the tissues outside the target area. Objectives: To observe the antagonism of dexamethasone on radiation bystander effect and its Re-transmission. Materials and methods: After 6MV X-ray irradiation of rabbit, the plasma, the first generation conditioned medium, was prepared to treat rabbit lymphocyte, cultured for 24 hours, 24 hours later, lymphocytes were collected, and the second generation conditioned medium was prepared with the lymphocyte secretion to treat new rabbit lymphocyte, and the apoptotic rate of effecter lymphocyte was detected. Dexamethasone was used as a parallel treatment control in all experimental groups. Results: The first and second generations of conditioned medium can stimulate lymphocyte apoptosis. Dexamethasone could reduce the apoptotic level of rabbit lymphocytes treated with the first and second generation bystander conditioned medium from 21.087% to 14.957%, 28.695% to 20.205%, respectively. Conclusion: Under certain conditions, dexamethasone can antagonize the injury of lymphocyte by radiation bystander effect, and can also antagonize the re-transmission of radiation bystander effect.

To observe the retransmission of radiation side effects between cells. [Materials and Methods] The mouse ovarian cancer cell line NUTU19 was irradiated with 6MV-X-rays, and the culture medium was prepared for the first-generation conditioned medium. The first-generation effector cells were used to detect the NUTU19 cell line and the intestinal mucosal epithelial IEC-6 cell line. The secretion of effector cells was a second-generation conditioned medium, and the second-generation effector cells NUTU19, IEC-6, and mouse lymphocytes were treated to measure cell viability and apoptosis. [Results] After treated with NUTU19 second-generation medium for 48 hours, the apoptosis rate of IEC-6 and NUTU19 cells was promoted (p>0.05), and the apoptosis rate of lymphocytes was decreased (p<0.05). After treatment with NUTU19 second-generation medium for 72 h, the apoptosis of NUTU19 and IEC-6 was promoted (p<0.05), and there was no effect on the apoptosis rate of lymphocytes (p>0.05). After treatment with IEC-6 second-generation medium for 48h, the apoptosis of NUTU19 and IEC-6 was promoted (p<0.05), and the apoptosis of lymphocytes was decreased (p<0.05). After treated with IEC-6 second-generation medium for 72h, there was no effect on IEC-6 and lymphocyte apoptosis (p>0.05). It promoted the apoptosis of NUTU19 (p<0.05). [Conclusion]: Under certain conditions, tumor cells, intestinal epithelial cells and lymphocytes can retransmit the damage of the side effect of radiation.