Office of Biological and Environmental Research

DOE Low Dose Radiation Program Workshop V

2005 Abstract

Title: The Radiation-induced Bystander Response: Different Protocols, Similar Effects.

Authors: C.R. Geard, A. Balajee, R. Baskar, G. Jenkins-Baker, A. Bigelow, S. Marino, and B. Ponnaiya.

Normal Human Fibroblasts (multiple origins) were exposed as hit cells and bystander cells, either in contact (site-specific Microbeam delivered alpha particles) or separated (track segment alpha particles and media transfer after low LET γ-irradiation). For each protocol there were dose-dependent increases in micronuclei (multiple assay points in situ) but non-dose-dependent increases in bystander cells (~2 fold). The p21/WAF1/cip1protein levels in individual cells was a sentinel marker of response in bystander cells. There were indications that all non-hit cells could respond to bystander signals. All single cell assays (for both mRNA and protein) demonstrated substantial inter-cell variability. These results support similar mechanisms for initiation of bystander responses under different experimental protocols.

This work was supported by the U.S. DOE’s Low Dose Radiation Research Program under Contract No. DE-FG 0298ER62687 and Department of Health and Human Services P41, RR-11623 (RARAF).