Adriamycin-induced oxidative stress, activation of MAP kinases and apoptosis in isolated cardiomyocytes.
BACKGROUND
Adriamycin (ADR) induced heart failure is associated with an increase in oxidative stress and apoptosis. Changes due to ADR in mitogen-activated protein kinases (ERK1/2 and p38 MAPKs), pro- and anti-apoptotic proteins (Bax and Bcl-xl) and apoptosis were examined in isolated adult rat cardiomyocytes.


METHODS
Isolated adult rat cardiomyocytes were exposed to different concentrations of ADR (0.1, 1 and 10mumol/L) and analyzed at different post-treatment durations. Antioxidant, trolox (20mumol/L) was used to determine involvement of oxidative stress on these changes.


RESULTS
Total ERK1/2 and p38 did not show any significant change. However, phosphorylated ERK1/2 showed a rapid increase (497%) after 5min of ADR treatment, peaking (610%) at 10min followed by a decline to submaximal levels at 30min (280%) and 60min (247%). Phosphorylated p38 showed no changes until after 30min, peaking (284%) at 1h, followed by a small decline at 2h. These changes were found to be dose-dependent (0.1, 1 and 10mumol/L of ADR). Adriamycin induced apoptosis was confirmed by Hoechst staining. The ratio of Bax/Bcl-xl increased in a dose-dependent manner. At 10mumol/L, this ratio increased to a maximum at 1h, remained steady at the level for up to 12h, followed by a decline below the base line at 24h. Antioxidant, trolox modulated the ADR-induced increase in phosphorylation of ERK1/2 and p38 MAPKs as well as in the ratio of Bax/Bcl-xl.


CONCLUSIONS
It is suggested that ADR activates MAP kinases, followed by an activation of pro-apoptotic protein Bax which results in cardiomyocyte apoptosis and these effects appear to be mediated by ADR-induced oxidative stress.
Institute of Cardiovascular Sciences, Department of Physiology, St. Boniface General Hospital Research Center, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
Huiquan
H
Lou
Kuljeet
K
Kaur
Anita K
AK
Sharma
Pawan K
PK
Singal