Atrogin-1 ubiquitin ligase is upregulated by doxorubicin via p38-MAP kinase in cardiac myocytes.
OBJECTIVE
Doxorubicin (DOX) is one of the most effective anti-neoplastic agents; however, its clinical use is limited by drug-induced cardiomyopathy. The molecular mechanisms responsible for this toxicity remain to be fully addressed. In the present study, we investigated the involvement of atrogin-1, one of the muscle-specific ubiquitin ligases, in DOX-induced cardiotoxicity.


RESULTS
This method involved intraperitoneal administration of DOX-induced atrogin-1 in the hearts and skeletal muscles of C57BL/6 mice. Consistently, atrogin-1 mRNA was upregulated with DOX treatment in cultured rat neonatal cardiomyocytes. Adenoviral transfer of atrogin-1 induced a reduction in cell size that was ameliorated by the ubiquitin proteasome inhibitor, MG-132. The transduction of constitutively active Akt (caAkt), a serine/threonine protein kinase, inhibited the DOX-mediated induction of atrogin-1. The phosphorylation status of Akt and its downstream target, FOXO, was not affected by DOX. DOX treatment did not activate the atrogin-1 promoter that contains FOXO-binding sites, suggesting that DOX induced atrogin-1 without modulating the Akt/FOXO pathway; importantly, DOX activated p38-mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK). Furthermore, pharmacological inhibition of p38-MAPK, but not JNK, abrogated DOX-mediated induction of atrogin-1. Finally, adenoviral transfer of caAkt inhibited the DOX-induced p38-MAPK activation.


CONCLUSIONS
DOX induces atrogin-1 through a p38-MAPK-dependent pathway in cardiac myocytes. Constitutive activation of Akt negatively regulates DOX-mediated atrogin-1 induction by inhibiting p38-MAPK activity as a novel mechanism.
Yamamoto
Yasuhiro
Y
Department of Clinical Pharmacology and Pharmacogenomics, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka565-0871, Japan.
Hoshino
Yuki
Y
Ito
Takashi
T
Nariai
Tetsuro
T
Mohri
Tomomi
T
Obana
Masanori
M
Hayata
Nozomi
N
Uozumi
Yoriko
Y
Maeda
Makiko
M
Fujio
Yasushi
Y
Azuma
Junichi
J
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000009:adverse effects / Q000494:pharmacology*; D001284:Atrophy; D009202:Cardiomyopathies / Q000139:chemically induced; D002478:Cells, Cultured; D004317:Doxorubicin / Q000009:adverse effects / Q000494:pharmacology*; D018014:Gene Transfer Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009124:Muscle Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000201:enzymology* / Q000473:pathology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D044843:SKP Cullin F-Box Protein Ligases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D000903:Antibiotics, Antineoplastic; D009124:Muscle Proteins; D004317:Doxorubicin; C486692:Fbxo32 protein, rat; D044843:SKP Cullin F-Box Protein Ligases; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases