Evaluation of Apoptosis with 99mTc-rhAnnexin V-128 and Inflammation with 18F-FDG in a Low-Dose Irradiation Model of Atherosclerosis in Apolipoprotein E-Deficient Mice.
Low-dose radiation in apolipoprotein E-deficient (ApoE-/-) mice has a protective effect with less subsequent atherosclerosis. Inflammation and apoptosis play major roles in the development of atherosclerosis. We evaluated the temporal pattern of the development of histologic atherosclerosis, inflammation with18F-FDG, and apoptosis with99mTc-rhAnnexin V-128 at 3 time points.


METHODS
ApoE-/-mice were fed a high-fat diet, exposed to low-dose60Co γ-radiation of 25 mGy at 2 mo of age, and evaluated within 1 wk (2-mo group), 1 mo (3-mo group), and 2 mo (4-mo group) from the time of radiation. Mice were divided into 3 subgroups and each received18F-FDG,99mTc-rhAnnexin V-128, or no radiotracer for autoradiography. Mice underwent euthanasia and aortic root dissection. The extent of atherosclerosis was determined by en face and Oil red O imaging. Aortic arch inflammation (18F-FDG) and apoptosis (99mTc-rhAnnexin V-128) were determined with digital autoradiography. Aortic sinus sections were stained with Sudan IV for assessment of lesion area and stage, antiCD68 antibody for inflammation and anti-cleaved-caspase 3 antibody for apoptosis.


RESULTS
The extent of aortic atherosclerosis increased from 2 to 3 mo and from 3 to 4 mo. Inflammation (CD68) decreased and apoptosis (anti-cleaved-caspase 3 antibody) increased in aortic sinus slices measured as percentage of lesion by 4 mo. With increasing lesion stage, lesion inflammation decreased and lesion apoptosis increased. Aortic arch inflammation (18F-FDG uptake) did not differ over time and did not correlate with average lesion stage. However, aortic arch apoptosis (99mTc-rhAnnexin V-128) increased significantly by 4 mo and correlated with average lesion stage. There were no differences between the treatment subgroups (18F-FDG,99mTc-rhAnnexin V-128, or no radiotracer).


CONCLUSIONS
The temporal pattern of development of inflammation and apoptosis differ during the development of atherosclerosis in ApoE-/-mice treated with low-dose radiation. Advanced lesions are characterized by increased apoptosis and either less or similar amounts of inflammation, shown on immunohistochemistry and autoradiography. Treatment with radiotracers had no significant effects on extent of atherosclerosis, inflammation, or apoptosis.
Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Canada.
Maryam
M
Kamkar
Nordion, Inc., Kanata, Canada; and.
Lihui
L
Wei
Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Canada.
Chantal
C
Gaudet
Radiological Protection Research and Instrumentation Branch, Canadian Nuclear Laboratories, Chalk River, Canada.
Michelle
M
Bugden
Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Canada.
Julia
J
Petryk
Nordion, Inc., Kanata, Canada; and.
Yin
Y
Duan
Radiological Protection Research and Instrumentation Branch, Canadian Nuclear Laboratories, Chalk River, Canada.
Heather M
HM
Wyatt
Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Canada.
R Glenn
RG
Wells
Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Canada.
Yves L
YL
Marcel
Radiological Protection Research and Instrumentation Branch, Canadian Nuclear Laboratories, Chalk River, Canada.
Nicholas D
ND
Priest
Radiological Protection Research and Instrumentation Branch, Canadian Nuclear Laboratories, Chalk River, Canada.
Ronald E J
RE
Mitchel
Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Canada truddy@ottawaheart.ca.
Terrence D
TD
Ruddy
D000818:Animals; D017304:Annexin A5; D001057:Apolipoproteins E / Q000235:genetics; D017209:Apoptosis / Q000528:radiation effects*; D050197:Atherosclerosis / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000473:pathology; D004307:Dose-Response Relationship, Radiation; D005260:Female; D019788:Fluorodeoxyglucose F18; D051379:Mice; D018345:Mice, Knockout; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D014657:Vasculitis / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000473:pathology; D014916:Whole-Body Irradiation / Q000009:adverse effects*
D017304:Annexin A5; D001057:Apolipoproteins E; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C417036:technetium Tc 99m annexin V; D019788:Fluorodeoxyglucose F18
18F-fluorodeoxyglucose; 99mTc-rhAnnexin V-128; atherosclerosis; autoradiography