Investigation of the bystander effect in MRC5 cells after acute and fractionated irradiation in vitro

Abstract

Radiation-induced bystander effect (RIBE) has been defined as radiation responses observed in nonirradiated cells. It has been the focus of investigators worldwide due to the deleterious effects it induces in nonirradiated cells. The present study was performed to investigate whether acute or fractionated irradiation will evoke a differential bystander response in MRC5 cells. A normal human cell line (MRC5), and a human lung tumor cell line (QU-DB) were exposed to 0, 1, 2, and 4Gy of single acute or fractionated irradiation of equal fractions with a gap of 6 h. The MRC5 cells were supplemented with the media of irradiated cells and their micronucleus frequency was determined. The micronucleus frequency after single and fractionated irradiation did not vary significantly in the MRC5 cells conditioned with autologous or QU-DB cell-irradiated media, except for 4Gy where the frequency of micronucleated cells was lower in those MRC5 cells cultured in the media of QU-DB-exposed with a single dose of 4Gy. Our study demonstrates that the radiation-induced bystander effect was almost similar after single acute and fractionated exposure in MRC5 cells.

The role of connexin proteins and their channels in radiation-induced atherosclerosis

“…These studies showed that RIBE depends on radiation quality, radiation dose, and dose rate used. RIBE was also reported in response to fractionated irradiation exposure commonly used in radiotherapy, which appears to be dependent on cell type, dose/dose rate, and the interval between fractions [ 61 , 62 ].…”

Radiation Induced Bystander Effect: From <i>in Vitro</i> Studies to Clinical Application

“…Thus bystander effect, if it appears in vivo during fractionated radiotherapy may reduce the expected sparing effect of fractionation to adjacent tissues and even increase normal tissue damage. On the other hand, no differences were observed in micronuclei induction in normal human lung fibroblasts (MRC5) treated with conditioned medium harvested from cultures of the same line or human lung tumor cell line (QU-DB) previously exposed to 1, 2, and 4 Gy of single acute or fractionated irradiation by equal fractions with a gap of 6 h [40]. It seems that human normal fibroblasts are relatively weak recipients of bystander signaling, especially when conditioned medium is harvested shortly after irradiation.…”

Radiation-induced Non-targeted Effect and Carcinogenesis; Implications in Clinical Radiotherapy

“…Another study did not show any differences in the frequency of micronucleus between a single acute dose and the fractionated one [23]. It is proposed that the effect of fractionation on the bystander effect response hinges on the radiation dose and seems to be obvious in higher doses [24].…”