Ratio of γ-H2AX level in lymphocytes to that in granulocytes detected using flow cytometry as a potential biodosimeter for radiation exposure

Biodosimetry Based on Gamma-H2AX Quantification in Human Peripheral Blood Lymphocytes after Partial-body Irradiation

ABSTRACT

Quantification of gamma-H2AX foci can estimate exposure to ionizing radiation. Most nuclear and radiation accidents are partial-body irradiation, and the doses estimated using the total-body irradiation dose estimation formula are often lower than the actual dose. To evaluate the dose-response relation of gamma-H2AX foci in human peripheral blood lymphocytes after partial-body irradiation and establish a simple and high throughput model to estimate partial-body irradiation dose, we collected human peripheral blood and irradiated with 0-, 0.5-, 1-, 2-, 3-, 4-, 5-, 6-, and 8-Gy gamma rays to simulate total-body irradiation in vitro. Gamma-H2AX foci were quantitated by flow cytometry at 1 h after irradiation, and a dose-response curve was established for total-body irradiation dose estimation. Then, a partial-body irradiation dose-response calibration curve was established by adding calibration coefficients based on the Dolphin method. To reflect the data distribution of all doses more realistically, the partial-body irradiation dose-response calibration curve was divided into two sections. In addition, partial-body irradiation was simulated in vitro, and the PBI data were substituted into curves to verify the accuracy of the two partial-body irradiation calibration curves. Results showed that the dose estimation variations were all less than 30% except the 25% partial-body irradiation group at 1 Gy, and the partial-body irradiation calibration dose-response curves were YF 1 = - 3.444 x 2 + 18.532 x + 3.109, R 2 = 0.92 (YF ≤ 27.95); YF 2 = - 2.704 x 2 + 37.97 x - 56.45, R 2 = 0.86 (YF > 27.95). Results also suggested that the partial-body irradiation dose-response calibration curve based on the gamma-H2AX foci quantification in human peripheral blood lymphocytes is a simple and high throughput model to assess partial-body irradiation dose.

An estimate assay for low-level exposure to ionizing radiation based on mass spectrometry quantification of γ-H2AX in human peripheral blood lymphocytes

Exposure to environmental ionizing radiation (IR) is ubiquitous, and large-dose exposure to IR is known to cause DNA damage and genotoxicity which is associated with an increased risk of cancer. Whether such detrimental effects are caused by exposure to low-dose IR is still debated. Therefore, rapid and early estimation of absorbed doses of IR in individuals, especially at low levels, using radiation response markers is a pivotal step for early triage during radiological incidents to provide adequate and timely clinical interventions. However, there is currently a crucial shortage of methods capable of determining the extent of low-dose IR exposure to human beings. The phosphorylation of histone H2AX on serine 139 (designated γ-H2AX), a classic biological dosimeter, can be used to evaluate the DNA damage response. We have developed an estimation assay for low-level exposure to IR based on the mass spectrometry quantification of γ-H2AX in blood. Human peripheral blood lymphocytes sensitive to low-dose IR, maintaining low temperature (4°C) and adding enzyme inhibitor are proven to be key steps, possibly insuring that a stable and marked γ-H2AX signal in blood cells exposed to low-dose IR could be detected. For the first time, DNA damage at low dose exposures to IR as low as 0.01 Gy were observed using the sensitive variation of γ-H2AX with high throughput mass spectrometry quantification in human peripheral blood, which is more accurate than the previously reported methods by virtue of isotope-dilution mass spectrometry, and can observe the time effect of DNA damage. These in vitro cellular dynamic monitoring experiments show that DNA damage occurred rapidly and then was repaired slowly over the passage of post-irradiation time even after exposure to very low IR doses. This assay was also used to assess different radiation exposures at the in vitro cellular level. These results demonstrate the potential utility of this assay in radiation biodosimetry and environmental risk assessment.

Haptoglobin is an early indicator of survival after radiation-induced severe injury and bone marrow transplantation in mice

Background

Hematopoietic stem cell transplantation (HSCT) is the main treatment for acute radiation sickness, especially after fatal radiation. The determination of HSCT for radiation patients is mainly based on radiation dose, hemogram and bone marrow injury severity. This study aims to explore a better biomarker of acute radiation injury from the perspective of systemic immune response.

Methods

C57BL/6J female mice were exposed to total body irradiation (TBI) and partial body irradiation (PBI). Changes in haptoglobin (Hp) level in plasma were shown at different doses and time points after the exposure and treatment with amifostine or bone marrow transplantation. Student’s t-test/two tailed test were used in two groups. To decide the Hp levels as a predictor of the radiation dose in TBI and PBI, multiple linear regression analysis were performed. The ability of biomarkers to identify two groups of different samples was determined by the receiver operating characteristic (ROC) curve. The results were expressed as mean ± standard deviation (SD). Significance was set at P value < 0.05, and P value < 0.01 was set as highly significant. Survival distribution was determined by log-rank test.

Results

In this study, we found that Hp was elevated dose-dependently in plasma in the early post-irradiation period and decreased on the second day, which can be used as a molecular indicator for early dose assessment. Moreover, we detected the second increase of Hp on the 3rd and 5th days after the lethal irradiation at 10 Gy, which was eliminated by amifostine, a radiation protection drug, while protected mice from death. Most importantly, bone marrow transplantation (BMT) on the 3rd and 5th day after 10 Gy radiation improved the 30-days survival rate, and effectively accelerated the regression of secondary increased Hp level.

Conclusions

Our study suggests that Hp can be used not only as an early molecule marker of radiation injury, but also as an important indicator of bone marrow transplantation therapy for radiation injury, bringing new scientific discoveries in the diagnosis and treatment of acute radiation injury from the perspective of systemic immunity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03162-x.

BPIFA2 as a Novel Early Biomarker to Identify Fatal Radiation Injury After Radiation Exposure

Background

Current dosimeters cannot cope with the two tasks of medical rescue in the early stage of nuclear accident, the accurate determination of radiation exposure and the identification of patients with fatal radiation injury. As radiation can cause alterations in serum components, it is feasible to develop biomarkers for radiation injury from serum. This study aims to investigate whether serum BPIFA2 could be used as a potential biomarker of predicting fatal radiation injury in the early stage after nuclear accident.

Methods

A rabbit anti-mouse BPIFA2 polyclonal antibody was prepared to detect the expression of BPIFA2. C57BL/6J female mice were exposed to total body radiation (TBI) at different dose and Partial body radiation (PBI) at lethal dose to detect the dynamic changes of BPIFA2 in serum at different time points after irradiation by Western blot assay.

Results

BPIFA2 in mice serum were significantly increased at 1–12 h post-irradiation at .5–10 Gy, and increased again significantly at 3 d after 10 Gy irradiation with associated with mortality closely. It also increased rapidly after PBI and was closely related to injury degree, regardless whether the salivary glands were irradiated.

Conclusions

The increase of serum BPIFA2 is a novel early biomarker not only for identifying radiation exposure, but also for fatal radiation injury playing a vital role in rational use of medical resources, and greater efficiency of medical treatment to minimize casualties.

Quantification of histone H2AX phosphorylation in white blood cells induced by ex vivo gamma irradiation of whole blood by both flow cytometry and foci counting as a dose estimation in rapid triage

A quick, reliable, and reproducible biological assay to distinguish individuals with possible life-threatening risk following radiological or nuclear incidents remains a quest in biodosimetry. In this paper, we examined the use of a γ-H2AX assay as an early dose estimation for rapid triage based on both flow cytometry and image analyses. In the experiment, whole blood from 11 donors was irradiated ex vivo inside a water phantom by gamma rays from Co-60 at 0.51 Gy/min. After the lysis of red blood cells, the white blood cells were collected for immunofluorescence labeling of γ-H2AX, CD45, and nuclear stained for signal collection and visualization. Analysis by flow cytometry showed that the relative γ-H2AX intensities of lymphocytes and granulocytes increased linearly with absorbed doses from 0 to 6 Gy with a large variation among individuals observed above 2 Gy. The relative γ-H2AX intensities of lymphocytes assessed by two different laboratories were highly correlated (ICC = 0.979). Using confocal microscopic images, γ-H2AX foci were observed to be discretely distributed inside the nuclei and to increase proportionally with doses from 0 to 2 Gy, whereas large plagues of merged foci appeared at 4 and 6 Gy, resulting in the saturation of foci counts above 4 Gy. The number of total foci per cell as well as the number of foci per plane were significantly different at 0 vs 1 and 2 vs 4 Gy doses (p < 0.01). Blind tests at 0.5 Gy and 1 Gy doses showed that dose estimation by flow cytometry had a mean absolute difference of less than 0.5 Gy from the actual value. In conclusion, while flow cytometry can provide a dose estimation with an uncertainty of 0.5 Gy at doses ≤ 1 Gy, foci counting can identify merged foci that are prominent at doses ≥ 4 Gy.

Early Biomarkers Associated with P53 Signaling for Acute Radiation Injury

Accurate dose assessment within 1 day or even 12 h after exposure through current methods of dose estimation remains a challenge, in response to a large number of casualties caused by nuclear or radiation accidents. P53 signaling pathway plays an important role in DNA damage repair and cell apoptosis induced by ionizing radiation. The changes of radiation-induced P53 related genes in the early stage of ionizing radiation should compensate for the deficiency of lymphocyte decline and γ-H2AX analysis as novel biomarkers of radiation damage. Bioinformatic analysis was performed on previous data to find candidate genes from human peripheral blood irradiated in vitro. The expression levels of candidate genes were detected by RT-PCR. The expressions of screened DDB2, AEN, TRIAP1, and TRAF4 were stable in healthy population, but significantly up-regulated by radiation, with time specificity and dose dependence in 2–24 h after irradiation. They are early indicators for medical treatment in acute radiation injury. Their effective combination could achieve a more accurate dose assessment for large-scale wounded patients within 24 h post exposure. The effective combination of p53-related genes DDB2, AEN, TRIAP1, and TRAF4 is a novel biodosimetry for a large number of people exposed to acute nuclear accidents.

Identification of Ferroptosis Biomarker in AHH-1 Lymphocytes Associated with Low Dose Radiation

ABSTRACT

The impact of long-term low-dose radiation on human health has always been a concern. Long-term low-dose gamma radiation causes cells continuous injury and causes chromosomal mutations to greatly increase the chance of cancer. Because it is significant to identify biomarkers for long-term low-dose gamma radiation, we investigate the influence of low dose rate on the gene expressions in the AHH-1 lymphocytes cell line (AHH-1 cells) for long-term irradiation. Different dose rates (7, 14, 26, 34, and 43 μGy h-1) of irradiation from gamma radiation in uranium tailings powder were used to irradiate AHH-1 lymphocytes. We used flow cytometry to test the apoptosis of AHH-1 lymphocytes at different dose rates and irradiation times (7-84 d). It was found that 14 μGy h-1 is the most sensitive dose rate of AHH-1 lymphocyte irradiation. The 7-, 14-, and 21-d (2.4, 4.8, and 7.2 mGy) irradiation groups were sensitive, and the 84-d (28.8 mGy) irradiation group was insensitive to low dose gamma radiation. Microarray analysis was conducted on the significantly differentially expressed genes (p<0.05) in the 2.4, 4.8, 7.2, and 28.8 mGy irradiation groups. We found that TFRC1, SLC3A2, SLC39A8, FTH1, ACSL4, and GPX4 are significant genes with low-dose radiation and were constituents of the ferroptosis signaling pathway. In the range of 0-4.8 mGy radiation dose, the expressions of these genes were downregulated with increasing radiation dose, while in the range of 4.8-28.8 mGy, its expression increased with increasing radiation dose. RT-PCR and Western blot were used to detect the mRNA and protein expression of these genes. The results were consistent with those from microarray analysis. Our findings indicate that expression of the TFRC, SLC3A2, SLC39A, FTH1, ACSL4, and GPX4 genes is sensitive to low-dose radiation, and they are main members of the ferroptosis signaling pathway. Therefore, there is a very important connection between ferroptosis and low-dose radiation, which has become a hot topic in international research. These results can provide reference to the effect of ferroptosis on human health with low-dose radiation.

Development of a high-throughput γ-H2AX assay based on imaging flow cytometry

Background

Measurement of γ-H2AX foci levels in cells provides a sensitive and reliable method for quantitation of the radiation-induced DNA damage response. The objective of the present study was to develop a rapid, high-throughput γ-H2AX assay based on imaging flow cytometry (IFC) using the ImageStream®^X Mk II (ISX) platform to evaluate DNA double strand break (DSB) repair kinetics in human peripheral blood cells after exposure to ionizing irradiation.

Methods

The γ-H2AX protocol was developed and optimized for small volumes (100 μL) of human blood in Matrix™ 96-tube format. Blood cell lymphocytes were identified and captured by ISX INSPIRE™ software and analyzed by Data Exploration and Analysis Software.

Results

Dose- and time-dependent γ-H2AX levels corresponding to radiation exposure were measured at various time points over 24 h using the IFC system. γ-H2AX fluorescence intensity at 1 h after exposure, increased linearly with increasing radiation dose (R² = 0.98) for the four human donors tested, whereas the dose response for the mean number of γ-H2AX foci/cell was not as robust (R² = 0.81). Radiation-induced γ-H2AX levels rapidly increased within 30 min and reached a maximum by ~ 1 h, after which time there was fast decline by 6 h, followed by a much slower rate of disappearance up to 24 h. A mathematical approach for quantifying DNA repair kinetics using the rate of γ-H2AX decay (decay constant, K_dec), and yield of residual unrepaired breaks (F_res) demonstrated differences in individual repair capacity between the healthy donors.

Conclusions

The results indicate that the IFC-based γ-H2AX protocol may provide a practical and high-throughput platform for measurements of individual global DNA DSB repair capacity which can facilitate precision medicine by predicting individual radiosensitivity and risk of developing adverse effects related to radiotherapy treatment.

Electronic supplementary material

The online version of this article (10.1186/s13014-019-1344-7) contains supplementary material, which is available to authorized users.

Study on γH2AX Expression of Lymphocytes as a Biomarker In Radiation Biodosimetry

Flow cytometry analysis was used to detect the changes of γH2AX protein expression in human peripheral blood lymphocytes. In the dose-effect study, the expression of γH2AX was detected 1 h after irradiation with 60Co γ-rays at doses of 0, 0.5, 1, 2, 4, and 6 Gy. Blood was cultivated for 0, 1, 2, 4, 6, 12, and 24 h after 4 Gy ⁶⁰Co γ-rays irradiation for the time-effect study. At the same time, the blood was divided into four treatment groups (ultraviolet [UV] irradiation, ⁶⁰Co γ-rays irradiation, UV plus ⁶⁰Co γ-rays irradiation, and control group) to detect the changes of protein expression of γH2AX. The results showed that the γH2AX protein expression was in dose-effect and time-effect relationship with ⁶⁰Co γ-rays. The peak expression of γH2AX was at 1 h after ⁶⁰Co γ-ray irradiation and began to decrease quickly. Compared to irradiation with ⁶⁰Co γ-rays alone, the expression of γH2AX was not significantly changed after irradiation with ⁶⁰Co γ-rays plus UV. Dose rate did not significantly change the expression of γH2AX. The expression of γH2AX induced by ⁶⁰Co γ-rays was basically consistent with the mice in vivo and in vitro. The results revealed that the detection of γH2AX protein expression changes in peripheral blood lymphocyte by flow cytometry analysis is reasonable and may be useful for biodosimetry.

The profiles of gamma-H2AX along with ATM/DNA-PKcs activation in the lymphocytes and granulocytes of rat and human blood exposed to gamma rays

Establishing a rat model suitable for γ-H2AX biodosimeter studies has important implications for dose assessment of internal radionuclide contamination in humans. In this study, γ-H2AX, p-ATM and p-DNA-PKcs foci were enumerated using immunocytofluorescence method, and their protein levels were measured by Western blot in rat blood lymphocytes and granulocytes exposed to γ-rays compared with human blood lymphocytes and granulocytes. It was found that DNA double-strand break repair kinetics and linear dose responses in rat lymphocytes were similar to those observed in the human counterparts. Moreover, radiation induced clear p-ATM and p-DNA-PKcs foci formation and an increase in ratio of co-localization of p-ATM or p-DNA-PKcs with γ-H2AX foci in rat lymphocytes similar to those of human lymphocytes. The level of γ-H2AX protein in irradiated rat and human lymphocytes was significantly reduced by inhibitors of ATM and DNA-PKcs. Surprisingly, unlike human granulocytes, rat granulocytes with DNA-PKcs deficiency displayed a rapid accumulation, but delayed disappearance of γ-H2AX foci with essentially no change from 10 h to 48 h post-irradiation. Furthermore, inhibition of ATM activity in rat granulocytes also decreased radiation-induced γ-H2AX foci formation. In comparison, human granulocytes showed no response to irradiation regarding γ-H2AX, p-ATM or p-DNA-PKcs foci. Importantly, incidence of γ-H2AX foci in lymphocytes after total-body radiation of rats was consistent with that of in vitro irradiation of rat lymphocytes. These findings show that rats are a useful in vivo model for validation of γ-H2AX biodosimetry for dose assessment in humans. ATM and DNA-PKcs participate together in DSB repair in rat lymphocytes similar to that of human lymphocytes. Further, rat granulocytes, which have the characteristic of delayed disappearance of γ-H2AX foci in response to radiation, may be a useful experimental system for biodosimetry studies.

Establishment of a γ-H2AX foci-based assay to determine biological dose of radon to red bone marrow in rats

The biodosimetric information is critical for assessment of cancer risk in populations exposed to high radon. However, no tools are available for biological dose estimation following radon exposure. Here, we established a γ-H2AX foci-based assay to determine biological dose to red bone marrow (RBM) in radon-inhaled rats. After 1–3 h of in vitro radon exposure, a specific pattern of γ-H2AX foci, linear tracks with individual p-ATM and p-DNA-PKcs foci, was observed, and the yield of γ-H2AX foci and its linear tracks displayed a linear dose-response manner in both rat peripheral blood lymphocytes (PBLs) and bone-marrow lymphocytes (BMLs). When the cumulative doses of radon inhaled by rats reached 14, 30 and 60 working level months (WLM), the yields of three types of foci markedly increased in both PBLs and BMLs, and γ-H2AX foci-based dose estimates to RBM were 0.97, 2.06 and 3.94 mGy, respectively. Notably, BMLs displayed a more profound increase of three types of foci than PBLs, and the absorbed dose ratio between BMLs and PBLs was similar between rats exposed to 30 and 60 WLM of radon. Taken together, γ-H2AX foci quantitation in PBLs is able to estimate RBM-absorbed doses with the dose-response curve of γ-H2AX foci after in vitro radon exposure and the ratio of RBM- to PBL-absorbed doses in rats following radon exposure.

Mean frequency and relative fluorescence intensity measurement of γ-H2AX foci dose response in PBL exposed to γ-irradiation: An inter- and intra-laboratory comparison and its relevance for radiation triage

Measurement of γ-H2AX protein changes in the peripheral blood lymphocytes (PBL) of individuals exposed to ionizing radiation is a simple, sensitive, and rapid assay for radiation triage and early marker of dose estimation. The qualitative and quantitative measurements of the protein changes were examined using flow cytometry and microscopy. Whole blood and isolated lymphocytes were exposed in vitro between 0.1 and 5 Gy doses of (60) Co γ-radiation at a dose rate of 1 Gy/min. Radiation induced γ-H2AX foci frequency (n = 3) and relative fluorescence intensity (n = 7) in PBL was measured at 0.5 and 2 hrs postexposure. The observed dose response for γ-H2AX foci frequency at both time points, for whole blood and isolated lymphocytes did not show any significant (P > 0.05) differences. However, when compared with γ-H2AX foci frequency scored manually (microscopy), the semiautomated analysis (captured images) showed a better correlation (r(2) = 0.918) than that obtained with automated (Metafer) scoring (r(2) = 0.690). It is noteworthy to mention that, the γ-H2AX foci frequency quantified using microscopy showed a dose dependent increase up to 2 Gy and the relative fluorescence intensity (RFI) measured with flow cytometry revealed an increase up to 5 Gy in the PBL exposed in vitro. Moreover, a better correlation was observed between the γ-H2AX foci frequency obtained by manual scoring and RFI (r(2) = 0.910). Kinetic studies showed that the γ-H2AX foci remain more or less unchanged up to 4 hrs and reduces gradually over 48 hrs of postexposure at 37°C. Further, inter and intra-laboratory comparisons showed consistency in the scoring of γ-H2AX foci frequency by manual and semiautomated scoring. The overall results suggest that measurement of γ-H2AX (microscopy and flow cytometry) should be employed within 4 to 6 hrs for a reliable dosimetry either by sharing the work load between the laboratories or investing more manpower; however, triage can be possible even up to 48 hrs of postirradiation.

Imaging flow cytometry as a sensitive tool to detect low-dose-induced DNA damage by analyzing 53BP1 and γH2AX foci in human lymphocytes

Ionizing radiation induced foci (IRIF) are considered the most sensitive indicator for DNA double-strand break (DSB) detection. Monitoring DSB induction by low doses of ionizing radiation is important due to the increasing exposure in the general population. γH2AX and 53BP1 are commonly used molecular markers for in situ IRIF assessment. Imaging flow cytometry (IFC) via ImageStream system provides a new opportunity in this field. We analyzed the formation of 53BP1, γH2AX foci and their co-localization induced by γ-rays (2, 5, 10, 50, 200 cGy) in human lymphocytes using ImageStream and the automated microscopic system Metafer. We observed very similar sensitivity of both systems for the detection of endogenous and low-dose-induced IRIF. Statistically significant induction of γH2AX foci was found at doses of 2 and 10 cGy using ImageStream and Metafer, respectively. Statistically significant induction of 53BP1 foci was evident at doses ≥ 5 cGy when analyzed by IFC. Analysis of the co-localizing foci by ImageStream and Metafer showed statistical significance at doses ≥ 2 cGy, suggesting that foci co-localization is a sensitive parameter for DSB quantification. Assessment of γH2AX, 53BP1 foci and their co-localization by Metafer and ImageStream showed similar linear dose responses in the low-dose range up to 10 cGy, although IFC showed slightly better resolution for IRIF in this dose range. At higher doses, IFC underestimated IRIF numbers. Using the imaging ability of ImageStream, we introduced an optimized assay by gating γH2AX foci positive (with 1 or more γH2AX foci) and negative (cells without foci) cells. This assay resulted in statistically significant IRIF induction at doses ≥ 5cGy and a linear dose response up to 50 cGy. In conclusion, we provide evidence for the use of IFC as an accurate high throughput assay for the prompt detection and enumeration of endogenous and low-dose induced IRIF.

Development of a multiparameter flow cytometric assay as a potential biomarker for homologous recombination deficiency in women with high-grade serous ovarian cancer

OBJECTIVES

PARP inhibitors (PARPi) are a novel class of drugs with activity in patients with acquired or germline homologous recombination (HR) deficiency-associated high-grade serous ovarian cancer (HGSOC). We hypothesized that measuring γH2AX as an indicator of DNA double-strand breaks (DSB), and MRE11 or RAD51 as an indicator of DSB repair, would reflect HR status and predict response to PARPi-based therapy. Our aim was to develop and use high-throughput multiparametric flow cytometry to quantify γH2AX with MRE11 or RAD51 in PBMCs as a readily available surrogate.

METHODS

Healthy donor PBMCs were used for assay development and optimization. We validated induction of γH2AX, MRE11 and RAD51 by staining with fluorophore-conjugated antibodies. The multiparameter flow cytometric method was applied to PBMC samples from recurrent HGSOC patients who were treated with PARPi, olaparib and carboplatin.

RESULTS

Stimulation was necessary for quantification of a DNA damage response to olaparib/carboplatin in healthy donor PBMCs. The flow cytometric protocol could not distinguish between cytoplasmic and nuclear RAD51, erroneously indicating activation in response to injury. Thus, MRE11 was selected as the marker of DSB repair. PBMCs from 15 recurrent HGSOC patients were then examined. Patients who did not respond to PARPi therapy had a significantly higher pre-treatment level of γH2AX (p = 0.01), and a higher ratio of γH2AX/MRE11 (11.0 [3.5-13.2] v. 3.3 [2.8-9.9], p < 0.03) compared with responders.

CONCLUSIONS

We successfully developed and applied a multiparameter flow cytometry assay to measure γH2AX and MRE11 in PBMCs. Prospective studies will be required to validate this surrogate biomarker assay as a potential predictive biomarker of PARPi-based therapy.