Characteristics of the adaptive response in cultured salmon cells exposed to ionizing radiation

Abstract

The aim of this study was to investigate the influence of "priming" doses of ionizing irradiation on salmon cell survival in vitro prior to being challenged with subsequent higher doses. A radiation-induced adaptive response (AR) was examined in the Chinook salmon embryo cell line (CHSE-214). Cells were initially irradiated with a range of priming (conditioning) doses of (60)Co gamma (gamma) rays (0.25-0.75 Gy), followed by a challenge dose of 7.50 Gy at intervals of 24, 48, and 72 hr. The AR was assessed using a colony-forming assay. Cell survival was determined by counting the number of colonies (viable clones) after 40 days of culture. This study revealed that cells that received a priming dose of 0.50 Gy before delivering the higher challenge dose became more radiation resistant with an increase in cell survival of 29% over cells receiving the challenge dose alone. The cells showed maximum resistance to ionizing radiation when the priming dose was given 72 hr prior to the higher challenge dose. This study is one of the first to demonstrate an AR using an in vitro piscine system, and is generally consistent with other studies of both in vitro and in vivo systems across the taxa.

Insights on the Radiation-Induced Adaptive Response at the Cellular Level and Its Implications in Cancer Therapy

“…Each marker has advantages and disadvantages in radiation biology studies. Clonogenic survival [37,68], or yields of CA [3], or SCE [69], or MN [36,67], or γ-H2AX foci, or HPRT mutations [39], as well as changes in proteins [38] or cell proliferation rate [61] have been extensively used to measure the effect induced after both AD and CD. Table 1 summarizes the various studies that examined the RIAR, the model employed, and the type of radiation used to examine the effect reported in the literature, which are included in this review.…”

“…Moreover, the percentage of attenuated damage was higher in cells grown in a 3D microenvironment than in a monolayer, implying that the culture conditions/environment influence the RIAR [38]. Observations of RIAR in most studies in normal cells seem advantageous, as the PD exposures followed by CD exposures make the cells adapt and protect them by increasing cell survival [37]. Cell lines from human and animal origin exhibit the RIAR phenomena upon exposure to β-, γ-, and X-rays; moreover, the magnitude depends upon the origin and 2D/3D culture environment.…”

“…Heterogeneity in the induction and magnitude of RIAR was observed among human lymphoblastoid cells; six out of 10 cell lines showed RIAR using MN formation upon exposure to PD of 0.05 Gy and then to 2 Gy of γ-rays with a time gap of 6 h [36]. About 22% increase in cell survival was observed in the chinook salmon embryonic cell line (CHSE-214) with an exposure of 0.5 Gy (PD) of γ-rays followed by exposure to a CD of 10 Gy γ-radiation [37]. Fibroblasts from human (RMP-4 and IMR-90) and mouse embryos were cultured both under monolayer and three-dimensional (3D) conditions and pre-treated with a PD (up to 100 mGy of X-rays) followed by CD (2 Gy of X-rays), which showed an attenuated level of γ-H2AX and p53 Ser−15 expression than cells exposed to CD alone.…”

Biologic Impact of Different Ultra-Low-Fluence Irradiations in Human Fibroblasts

“…This radio-adaptive response was first described as reduced frequency of X-ray-induced chromosomal aberrations in stimulated human lymphocytes co-cultured with radioactive 3 H-thymidine [ 10 ]. Subsequently, radio-adaptive responses have been reported in several biologic settings [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. A similar adaptive response has also been reported in clinical settings, in patients undergoing treatments for thyroid diseases [ 19 ].…”