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γ-H2AX Kinetic Profile in Mouse Lymphocytes Exposed to the Internal Emitters Cesium-137 and Strontium-90.

Turner HC, Shuryak I, Weber W, Doyle-Eisele M, Melo D, Guilmette R, Amundson SA, Brenner DJ - PLoS ONE (2015)

Bottom Line: In order to measure the kinetic profile for γ-H2AX, peripheral blood samples were drawn at 5 specific timed dose points over the 30-day study period and the total γ-H2AX nuclear fluorescence per lymphocyte was determined using image analysis software.A mechanistically-motivated model was used to analyze the temporal kinetics of γ-H2AX fluorescence.The complexity of the observed responses to internal irradiation is likely caused by the interplay between continual production and repair of DNA damage, cell cycle effects and apoptosis.

View Article: PubMed Central - PubMed

Affiliation: Center for Radiological Research, Columbia University Medical Center, New York, New York, United States of America.

ABSTRACT
In the event of a dirty bomb scenario or an industrial nuclear accident, a significant dose of volatile radionuclides such as 137Cs and 90Sr may be dispersed into the atmosphere as a component of fallout and inhaled or ingested by hundreds and thousands of people. To study the effects of prolonged exposure to ingested radionuclides, we have performed long-term (30 day) internal-emitter mouse irradiations using soluble-injected 137CsCl and 90SrCl2 radioisotopes. The effect of ionizing radiation on the induction and repair of DNA double strand breaks (DSBs) in peripheral mouse lymphocytes in vivo was determined using the γ-H2AX biodosimetry marker. Using a serial sacrifice experimental design, whole-body radiation absorbed doses for 137Cs (0 to 10 Gy) and 90Sr (0 to 49 Gy) were delivered over 30 days following exposure to each radionuclide. The committed absorbed doses of the two internal emitters as a function of time post exposure were calculated based on their retention parameters and their derived dose coefficients for each specific sacrifice time. In order to measure the kinetic profile for γ-H2AX, peripheral blood samples were drawn at 5 specific timed dose points over the 30-day study period and the total γ-H2AX nuclear fluorescence per lymphocyte was determined using image analysis software. A key finding was that a significant γ-H2AX signal was observed in vivo several weeks after a single radionuclide exposure. A mechanistically-motivated model was used to analyze the temporal kinetics of γ-H2AX fluorescence. Exposure to either radionuclide showed two peaks of γ-H2AX: one within the first week, which may represent the death of mature, differentiated lymphocytes, and the second at approximately three weeks, which may represent the production of new lymphocytes from damaged progenitor cells. The complexity of the observed responses to internal irradiation is likely caused by the interplay between continual production and repair of DNA damage, cell cycle effects and apoptosis.

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Related in: MedlinePlus

Median response pattern of γ-H2AX yields in peripheral blood mouse lymphocytes following 30-day internal exposures to 137Cs (dashed black line), high-dose 90Sr (solid red line) and low-dose 90Sr (solid blue line).The curves connecting the points are splines shown for convenience only, to guide the eye.
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pone.0143815.g002: Median response pattern of γ-H2AX yields in peripheral blood mouse lymphocytes following 30-day internal exposures to 137Cs (dashed black line), high-dose 90Sr (solid red line) and low-dose 90Sr (solid blue line).The curves connecting the points are splines shown for convenience only, to guide the eye.

Mentions: Gamma H2AX foci were detected by indirect immunostaining and quantified by fluorescence intensity relative to the unirradiated control cells. Fig 2 shows the median γ-H2AX nuclear fluorescence values measured in lymphocytes at the specific time/dose points following the injection of the radionuclides. Because the fluorescence was recorded in arbitrary units, comparison of the γ-H2AX kinetics was assisted by normalizing the median γ-H2AX values for each radionuclide experiment as follows: each data point was divided by the highest value observed in the given experiment. For example, the highest median fluorescence value used for normalization occurred at day 7 for Sr (both high and low doses) and at day 4 for Cs. The γ-H2AX kinetic profile for 137Cs exposure (denoted by black dashed line) indicated that the γ-H2AX yields at Day 2 (total body committed absorbed dose = 1.95 Gy) showed the highest levels followed by a rapid decline in γ-H2AX frequency by Day 5 (total body committed absorbed dose = 4.14 Gy), after which time there is a gradual increase in the γ-H2AX frequency up to 30 Days. Although the results show that at Day 5 the γ-H2AX yields are significantly above non-irradiated baseline levels, the fact that there are no blood draws between Day 5 and Day 20 makes it difficult to determine at what the point the γ-H2AX yields continue to decrease or when they start to increase. For the 90Sr exposures, the high-dose 90Sr study data (denoted by solid red line) show that γ-H2AX yields appear to increase up to Day 7 (total skeletal committed absorbed dose = 20 Gy), after which there is a rapid decease in γ-H2AX levels by Day 9 (total skeletal committed absorbed dose = 28.5 Gy) with no apparent further increase over the remainder of the study. The γ-H2AX kinetic profile for low-dose 90Sr exposure (denoted by solid blue line) similarly showed that the total γ-H2AX fluorescence levels continue to increase up to Day 7 (total skeletal committed absorbed dose = 1.8 Gy), after which time there is apparent 50% drop in γ-H2AX levels. At some point between Day 9 and Day 25 the γ-H2AX protein levels started to increase leading to drop off in yields by Day 30. For all three studies, the median γ-H2AX values for the non-irradiated control lymphocyte samples measured over the 30-day study period are plotted at the time zero, 0 Gy data point.


γ-H2AX Kinetic Profile in Mouse Lymphocytes Exposed to the Internal Emitters Cesium-137 and Strontium-90.

Turner HC, Shuryak I, Weber W, Doyle-Eisele M, Melo D, Guilmette R, Amundson SA, Brenner DJ - PLoS ONE (2015)

Median response pattern of γ-H2AX yields in peripheral blood mouse lymphocytes following 30-day internal exposures to 137Cs (dashed black line), high-dose 90Sr (solid red line) and low-dose 90Sr (solid blue line).The curves connecting the points are splines shown for convenience only, to guide the eye.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664397&req=5

pone.0143815.g002: Median response pattern of γ-H2AX yields in peripheral blood mouse lymphocytes following 30-day internal exposures to 137Cs (dashed black line), high-dose 90Sr (solid red line) and low-dose 90Sr (solid blue line).The curves connecting the points are splines shown for convenience only, to guide the eye.
Mentions: Gamma H2AX foci were detected by indirect immunostaining and quantified by fluorescence intensity relative to the unirradiated control cells. Fig 2 shows the median γ-H2AX nuclear fluorescence values measured in lymphocytes at the specific time/dose points following the injection of the radionuclides. Because the fluorescence was recorded in arbitrary units, comparison of the γ-H2AX kinetics was assisted by normalizing the median γ-H2AX values for each radionuclide experiment as follows: each data point was divided by the highest value observed in the given experiment. For example, the highest median fluorescence value used for normalization occurred at day 7 for Sr (both high and low doses) and at day 4 for Cs. The γ-H2AX kinetic profile for 137Cs exposure (denoted by black dashed line) indicated that the γ-H2AX yields at Day 2 (total body committed absorbed dose = 1.95 Gy) showed the highest levels followed by a rapid decline in γ-H2AX frequency by Day 5 (total body committed absorbed dose = 4.14 Gy), after which time there is a gradual increase in the γ-H2AX frequency up to 30 Days. Although the results show that at Day 5 the γ-H2AX yields are significantly above non-irradiated baseline levels, the fact that there are no blood draws between Day 5 and Day 20 makes it difficult to determine at what the point the γ-H2AX yields continue to decrease or when they start to increase. For the 90Sr exposures, the high-dose 90Sr study data (denoted by solid red line) show that γ-H2AX yields appear to increase up to Day 7 (total skeletal committed absorbed dose = 20 Gy), after which there is a rapid decease in γ-H2AX levels by Day 9 (total skeletal committed absorbed dose = 28.5 Gy) with no apparent further increase over the remainder of the study. The γ-H2AX kinetic profile for low-dose 90Sr exposure (denoted by solid blue line) similarly showed that the total γ-H2AX fluorescence levels continue to increase up to Day 7 (total skeletal committed absorbed dose = 1.8 Gy), after which time there is apparent 50% drop in γ-H2AX levels. At some point between Day 9 and Day 25 the γ-H2AX protein levels started to increase leading to drop off in yields by Day 30. For all three studies, the median γ-H2AX values for the non-irradiated control lymphocyte samples measured over the 30-day study period are plotted at the time zero, 0 Gy data point.

Bottom Line: In order to measure the kinetic profile for γ-H2AX, peripheral blood samples were drawn at 5 specific timed dose points over the 30-day study period and the total γ-H2AX nuclear fluorescence per lymphocyte was determined using image analysis software.A mechanistically-motivated model was used to analyze the temporal kinetics of γ-H2AX fluorescence.The complexity of the observed responses to internal irradiation is likely caused by the interplay between continual production and repair of DNA damage, cell cycle effects and apoptosis.

View Article: PubMed Central - PubMed

Affiliation: Center for Radiological Research, Columbia University Medical Center, New York, New York, United States of America.

ABSTRACT
In the event of a dirty bomb scenario or an industrial nuclear accident, a significant dose of volatile radionuclides such as 137Cs and 90Sr may be dispersed into the atmosphere as a component of fallout and inhaled or ingested by hundreds and thousands of people. To study the effects of prolonged exposure to ingested radionuclides, we have performed long-term (30 day) internal-emitter mouse irradiations using soluble-injected 137CsCl and 90SrCl2 radioisotopes. The effect of ionizing radiation on the induction and repair of DNA double strand breaks (DSBs) in peripheral mouse lymphocytes in vivo was determined using the γ-H2AX biodosimetry marker. Using a serial sacrifice experimental design, whole-body radiation absorbed doses for 137Cs (0 to 10 Gy) and 90Sr (0 to 49 Gy) were delivered over 30 days following exposure to each radionuclide. The committed absorbed doses of the two internal emitters as a function of time post exposure were calculated based on their retention parameters and their derived dose coefficients for each specific sacrifice time. In order to measure the kinetic profile for γ-H2AX, peripheral blood samples were drawn at 5 specific timed dose points over the 30-day study period and the total γ-H2AX nuclear fluorescence per lymphocyte was determined using image analysis software. A key finding was that a significant γ-H2AX signal was observed in vivo several weeks after a single radionuclide exposure. A mechanistically-motivated model was used to analyze the temporal kinetics of γ-H2AX fluorescence. Exposure to either radionuclide showed two peaks of γ-H2AX: one within the first week, which may represent the death of mature, differentiated lymphocytes, and the second at approximately three weeks, which may represent the production of new lymphocytes from damaged progenitor cells. The complexity of the observed responses to internal irradiation is likely caused by the interplay between continual production and repair of DNA damage, cell cycle effects and apoptosis.

Show MeSH
Related in: MedlinePlus