Imaging features that discriminate between foci induced by high- and low-LET radiation in human fibroblasts.

Abstract

In this study, we investigated the formation of radiation-induced foci in normal human fibroblasts exposed to X rays or 130 keV/mum nitrogen ions using antibodies to phosphorylated protein kinase ataxia telangiectasia mutated (ATMp) and histone H2AX (gamma-H2AX). High-content automatic image analysis was used to quantify the immunofluorescence of radiation-induced foci. The size of radiation-induced foci increased for both proteins over a 2-h period after nitrogen-ion irradiation, while the size of radiation-induced foci did not change after exposure to low-LET radiation. The number of radiation-induced ATMp foci showed a more rapid rise and greater frequency after X-ray exposure and was resolved more rapidly such that the frequency of radiation-induced foci decreased by 90% compared to 60% after exposure to high-LET radiation 2 h after 30 cGy. In contrast, the kinetics of radiation-induced gamma-H2AX focus formation was similar for high- and low-LET radiation in that it reached a plateau early and remained constant for up to 2 h. High-resolution 3D images of radiation-induced gamma-H2AX foci and dosimetry computation suggest that multiple double-strand breaks from nitrogen ions are encompassed within large nuclear domains of 4.4 Mbp. Our work shows that the size and frequency of radiation-induced foci vary as a function of radiation quality, dose, time and protein target. Thus, even though double-strand breaks and radiation-induced foci are correlated, the dynamic nature of both contradicts their accepted equivalence for low doses of different radiation qualities.

• Authors: Sylvain V Costes, Arnaud Boissière, Shraddha Ravani, Raquel Romano, Bahram Parvin, Mary Helen Barcellos-Hoff
• Journal: Radiation research (Radiat Res) Vol. 165 Issue 5 Pg. 505-15 (May 2006) ISSN: 0033-7587 [Print] United States
• PMID: 16669704 (Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Cell Cycle Proteins
• DNA-Binding Proteins
• H2AX protein, human
• Histones
• Tumor Suppressor Proteins
• DNA
• ATM protein, human
• Ataxia Telangiectasia Mutated Proteins
• Protein Serine-Threonine Kinases

Topics

• Ataxia Telangiectasia Mutated Proteins
• Cell Cycle Proteins (genetics, radiation effects)
• Cells, Cultured
• DNA (radiation effects, ultrastructure)
• DNA Damage (genetics)
• DNA-Binding Proteins (genetics, radiation effects)
• Dose-Response Relationship, Radiation
• Fibroblasts (cytology, metabolism, radiation effects)
• Histones (genetics, radiation effects)
• Humans
• Image Interpretation, Computer-Assisted (methods)
• Linear Energy Transfer
• Micronucleus Tests (methods)
• Microscopy, Fluorescence (methods)
• Phosphorylation (radiation effects)
• Protein Serine-Threonine Kinases (genetics, radiation effects)
• Radiation Dosage
• Radiation, Ionizing
• Reproducibility of Results
• Sensitivity and Specificity
• Tumor Suppressor Proteins (genetics, radiation effects)