Doxorubicin treatment in vivo causes cytochrome C release and cardiomyocyte apoptosis, as well as increased mitochondrial efficiency, superoxide dismutase activity, and Bcl-2:Bax ratio.
There have been very few investigations as to whether mitochondrial-mediated apoptosis in vivo is the underlying mechanism of doxorubicin cardiotoxicity. Moreover, no investigations have been conducted to determine whether there are adaptive responses after doxorubicin treatment. We administered a single dose of doxorubicin (20 mg/kg) to male rats and isolated intact mitochondria from their hearts 4 days later. Apoptosis, as determined by the amount of cytosolic mononucleosomal and oligonucleosomal DNA fragments (180 bp or multiples), was significantly increased after doxorubicin treatment. In contrast, Troponin-T, a cardiac-specific marker for necrotic damage, was unaltered 4 days after doxorubicin treatment. Cytosolic cytochrome c increased 2-fold in the doxorubicin-treated rats and was significantly correlated (r = 0.88; P < 0.01) with the increase in caspase-3 activity observed. Moreover, the level of bleomyocin-detectable iron in serum was significantly increased and may have contributed to the increase in oxidative stress, which was indicated by an increase in cytosolic 8-iso prostaglandin F(2alpha). Cytosolic copper zinc superoxide dismutase activity also increased significantly further supporting the notion that doxorubicin increases superoxide radical production. In addition to adaptations to antioxidant defenses, other adaptive mechanisms occurred in the mitochondria such as an increase in the respiratory P/O ratio and an increase in the Bcl-2:Bax ratio. These findings demonstrate that doxorubicin induces oxidative stress and mitochondrial-mediated apoptosis, as well as adaptive responses by the mitochondria to protect cardiac myocytes in vivo.
University of Florida, Biochemistry of Aging Laboratory, College of Health and Human Performance, Gainesville, Florida 32611, USA.
April C
AC
Childs
Sharon L
SL
Phaneuf
Amie J
AJ
Dirks
Tracey
T
Phillips
Christiaan
C
Leeuwenburgh
D000595:Amino Acid Sequence; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000633:toxicity*; D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D003574:Cytochrome c Group / Q000378:metabolism*; D004317:Doxorubicin / Q000633:toxicity*; D006321:Heart / Q000033:anatomy & histology / Q000187:drug effects*; D007425:Intracellular Membranes / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D007501:Iron / Q000378:metabolism; D008297:Male; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000502:physiology; D008969:Molecular Sequence Data; D009206:Myocardium / Q000201:enzymology / Q000473:pathology; D009929:Organ Size / Q000187:drug effects; D018384:Oxidative Stress; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013482:Superoxide Dismutase / Q000378:metabolism*; D051028:bcl-2-Associated X Protein
D000903:Antibiotics, Antineoplastic; D000975:Antioxidants; C494828:Bax protein, rat; D003574:Cytochrome c Group; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D004317:Doxorubicin; D007501:Iron; D013482:Superoxide Dismutase