Oleandrin-mediated oxidative stress in human melanoma cells.
While certain cardiac glycoside compounds such as oleandrin, bufalin and digitoxin are known to be associated with potent cytotoxicity to human tumor cells, the mechanisms by which this effect is produced are not clear. We now demonstrate that incubation of human malignant melanoma BRO cells with oleandrin results in a time-dependent formation of reactive oxygen species (ROS). Use of Mito-SOX and dihydroethidine dyes revealed the presence of oleandrin-mediated superoxide anions. Formation of superoxide anions correlated with a loss in cellular viability, proliferation and cellular defense mechanisms such as GSH content. Oleandrin also resulted in an unusual time-dependent mitochondrial condensation in BRO cells that could be blocked with use of N-acetyl cysteine (NAC). NAC was also shown to block ROS formation and partially prevent oleandrin-mediated loss of cellular GSH. Taken as a whole, the data suggest that exposure of human tumor cells such as BRO to oleandrin results in the formation of superoxide anion radicals that mediate mitochondrial injury and loss of cellular GSH pools. These mechanisms play a role in cardiac glycoside mediated tumor cell injury. Conversely, incubation of NAC, a precursor to GSH, largely prevents oleandrin-mediated inhibition of proliferation and mitochondria structural changes.
Newman
Robert A
RA
Department of Experimental Therapeutics, Univ. Texas M. D. Anderson Cancer Center, Houston, TX 77054, USA. rnewman@mdanderson.org
Yang
Peiying
P
Hittelman
Walter N
WN
Lu
Tao
T
Ho
Dah Hsi
DH
Ni
Dan
D
Chan
Diana
D
Vijjeswarapu
Mary
M
Cartwright
Carrie
C
Dixon
Susan
S
Felix
Edward
E
Addington
Crandell
C
D002298:Cardenolides / Q000494:pharmacology*; D049109:Cell Proliferation; D003553:Cystine / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D008545:Melanoma / Q000188:drug therapy / Q000473:pathology*; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D018384:Oxidative Stress; D017382:Reactive Oxygen Species; D012878:Skin Neoplasms / Q000188:drug therapy / Q000473:pathology*; D014407:Tumor Cells, Cultured
D002298:Cardenolides; D017382:Reactive Oxygen Species; D003553:Cystine; C021065:oleandrin; C030905:N-monoacetylcystine