Analysis of radiation-induced apoptosis in human lymphocytes: flow cytometry using Annexin V and propidium iodide versus the neutral comet assay.
BACKGROUND
The neutral comet assay was devised to measure double-stranded DNA breaks, but it has also been used to measure apoptosis based on its characteristic DNA fragmentation patterns. There is still uncertainty about the reliability of this method. By comparing the comet assay with a flow cytometry method that uses Annexin V binding to apoptotic cells, we have provided further evidence for evaluating the usefulness of the comet assay for detecting apoptosis.


METHODS
Apoptosis was induced in human peripheral blood mononuclear cells (PBMC) by ionizing radiation and measured using the comet assay and a flow cytometry method that measures Annexin V and propidium iodide (PI) staining.


RESULTS
The Annexin V flow cytometry assay distinguished among early apoptosis, late apoptosis, and an apoptotic or necrotic phase in which the cells were labeled with both Annexin V and PI. The comet assay detected only the latter two phases of apoptosis.


CONCLUSIONS
The comet assay is a useful tool for measuring the late stages of apoptosis whereas the Annexin V assay measures higher amounts of apoptosis because it can detect cells in an earlier stage of the apoptotic pathway.
Consumer and Clinical Radiation Protection Bureau, Health Canada, 775 Brookfield Road, Postal Locator 6303B, Ottawa, Ontario K1A 1C1, Canada. Ruth_Wilkins@hc-sc.gc.ca
Ruth C
RC
Wilkins
B C
BC
Kutzner
M
M
Truong
J
J
Sanchez-Dardon
J R N
JR
McLean
D017304:Annexin A5 / Q000032:analysis; D017209:Apoptosis / Q000276:immunology / Q000528:radiation effects*; D004396:Coloring Agents; D020552:Comet Assay; D005434:Flow Cytometry; D006801:Humans; D008214:Lymphocytes / Q000737:chemistry / Q000166:cytology* / Q000528:radiation effects*; D011419:Propidium
D017304:Annexin A5; D004396:Coloring Agents; D011419:Propidium