The Use of Gamma-H2AX as a Biodosimeter for Total-Body Radiation Exposure in Non-Human Primates

Abstract

BackgroundThere is a crucial shortage of methods capable of determining the extent of accidental exposures of human beings to ionizing radiation. However, knowledge of individual exposures is essential for early triage during radiological incidents to provide optimum possible life-sparing medical procedures to each person.Methods and FindingsWe evaluated immunocytofluorescence-based quantitation of γ-H2AX foci as a biodosimeter of total-body radiation exposure (60Co γ-rays) in a rhesus macaque (Macaca mulatta) model. Peripheral blood lymphocytes and plucked hairs were collected from 4 cohorts of macaques receiving total body irradiation doses ranging from 1 Gy to 8.5 Gy. Each cohort consisted of 6 experimental and 2 control animals. Numbers of residual γ-H2AX foci were proportional to initial irradiation doses and statistically significant responses were obtained until 1 day after 1 Gy, 4 days after 3.5 and 6.5 Gy, and 14 days after 8.5 Gy in lymphocytes and until 1 day after 1 Gy, at least 2 days after 3.5 and 6.5 Gy, and 9 days after 8.5 Gy in plucked hairs.ConclusionThese findings indicate that quantitation of γ-H2AX foci may make a robust biodosimeter for analyzing total-body exposure to ionizing radiation in humans. This tool would help clinicians prescribe appropriate types of medical intervention for optimal individual outcome. These results also demonstrate that the use of a high throughput γ-H2AX biodosimeter would be useful for days post-exposure in applications like large-scale radiological events or radiation therapy. In addition, this study validates a possibility to use plucked hair in future clinical trials investigating genotoxic effects of drugs and radiation treatments.

Heat Shock Protein 90α (Hsp90α) Is Phosphorylated in Response to DNA Damage and Accumulates in Repair Foci

“…For immunofluorescence staining, cells were processed as described previously (19). Hair samples were prepared for immunohistochemistry as described previously (25). Microscopy was performed with the Leica SP5 confocal system, attached to a DMI6000 stand, with a 63ϫ/1.4 or 40ϫ/1.25 oil immersion objective.…”

“…First, ␥-H2AX quantification can be used to assess the efficacy of DNA damage-inducing chemo-or radiotherapy (25). Second, the spontaneous phosphorylation of H2AX has been reported to be a marker of genetic instability in tumors (54).…”

90Y-daclizumab, an anti-CD25 monoclonal antibody, provided responses in 50% of patients with relapsed Hodgkin’s lymphoma

“…One major outcome from radiation exposure is the formation of DNA double-strand breaks (DSBs). DSBs can be enumerated with a sensitive assay based on the immunohistochemical visualization of phosphorylated H2AX (γ-H2AX) (25)(26)(27)(28)(29). γ-H2AX immunostaining was enumerated in both malignant cells and surrounding nonmalignant cells in tumor biopsies before and 4-10 d after 90 Y-daclizumab infusions.…”

“…Use of γ-H2AX as a Bioindicator for the Exposure of HL Tissue to Radiation. γ-H2AX was used as a bioindicator of the effects on HL tissue of exposure to radiation using procedures described previously (25,26). (See SI Materials and Methods for further details.…”

Suitability of the γ-H2AX Assay for Human Radiation Biodosimetry

“…For doses greater than 1 Gy, a substantial response was detected in the lymphocytes for up to 2 days after exposure (Redon, 2009). These results -obtained visually-have been confirmed in vivo in non-human PBMCs after irradiation of macaques receiving total body γ-ray doses ranging from 1 Gy to 8.5 Gy, for times up to 4 days after exposure (Redon, 2010). Automatic systems may be used to avoid focus scoring bias that may prevent interlaboratory comparisons.…”