Annexin V imaging of acute doxorubicin cardiotoxicity (apoptosis) in rats.
Anthracyclines are widely used in chemotherapy regimens for several malignancies, with cardiotoxicity being the major limiting factor in high-dose schedules. Recently, it was reported that doxorubicin induces apoptosis in cardiac muscle cells in vivo and, as such, is expected to be involved in the genesis of doxorubicin-induced cardiomyopathy. The aim of this study was to validate an animal model for in vivo monitoring of doxorubicin cardiotoxicity by means of scintigraphic detection of apoptosis.


METHODS
Three groups of 5 male Wistar rats each were treated for 3, 4, and 5 times with a weekly intraperitoneal injection of doxorubicin at 2.5 mg/kg. At 24 h before and 24 h after the final treatment, (99m)Tc-annexin pinhole scintigraphy was performed. A control group of 5 rats was scanned without doxorubicin treatment. A cardiac uptake ratio was calculated from planar scintigraphy results with the following formula: (mediastinum - fat)/fat. After scintigraphy, the rats were sacrificed, and the heart was processed for histologic analysis.


RESULTS
Incremental general signs of illness were observed with increasing total cumulative doxorubicin dose. Rats treated for 3, 4, and 5 wk with doxorubicin showed significantly higher uptake ratios of, respectively, 4.0 +/- 0.52 (mean +/- SEM), 4.8 +/- 0.46, and 5.2 +/- 0.17 after the final treatment; the ratio for controls was 1.84 +/- 0.05 (P < 0.05). Histologic analysis confirmed cardiac stress in treated groups, with an increasing left ventricular atrial natriuretic factor messenger RNA expression level with increasing cumulative doxorubicin dose. Late apoptosis was confirmed by terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling in the rats treated for 5 wk.


CONCLUSIONS
Acute doxorubicin-induced cardiomyopathy based on early apoptosis can be assessed and imaged with annexin V scintigraphy in rats. This finding makes it possible to use this animal model for repetitive noninvasive evaluation of cardioprotective regimens for anthracycline cardiotoxicity.
Bennink
Roelof J
RJ
Department of Nuclear Medicine, Academic Medical Center, Amsterdam, The Netherlands. r.bennink@amc.uva.nl
van den Hoff
Maurice J
MJ
van Hemert
Formijn J
FJ
de Bruin
Kora M
KM
Spijkerboer
Astrid L
AL
Vanderheyden
Jean-Luc
JL
Steinmetz
Neil
N
van Eck-Smit
Berthe L
BL
D000818:Animals; D017304:Annexin A5; D000903:Antibiotics, Antineoplastic / Q000633:toxicity*; D017209:Apoptosis; D009320:Atrial Natriuretic Factor / Q000378:metabolism; D004317:Doxorubicin / Q000633:toxicity*; D006321:Heart / Q000187:drug effects*; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects*; D015609:Organotechnetium Compounds; D012333:RNA, Messenger / Q000235:genetics; D019275:Radiopharmaceuticals; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D017304:Annexin A5; D000903:Antibiotics, Antineoplastic; D015609:Organotechnetium Compounds; D012333:RNA, Messenger; D019275:Radiopharmaceuticals; C417036:technetium Tc 99m annexin V; D004317:Doxorubicin; D009320:Atrial Natriuretic Factor