Protection of doxorubicin cytotoxicity by cycloheximide.
The effect of cycloheximide (an inhibitor of cellular protein synthesis) on doxorubicin-induced cytotoxicity in V79 (rodent fibroblasts) cells was investigated. Cycloheximide is a potent protector of doxorubicin-induced cytotoxicity at concentrations paralleling those required for protein synthesis inhibition. The greatest protective effect was achieved at 10 microM cycloheximide; this concentration correlated with 95% inhibition of protein synthesis. A 15 minute cycloheximide (10 microM) exposure resulted in maximal protein synthesis inhibition; however, 4-6 hr of pretreatment with cycloheximide (10 microM) was required to maximally protect cells from doxorubicin. These results suggest that a time-dependent depletion of a protein is required for cycloheximide's protective effect. Cycloheximide treatments were found to decrease intracellular accumulation of doxorubicin by 35-50% but this decrease accounts for only a small fraction of the total protective effect. When corrections were made for differences in doxorubicin accumulation, cycloheximide had no effect on the formation of DNA-protein crosslinks (DNA-topoisomerase II complexes revealed as single strand DNA breaks in alkaline elution studies). These studies suggest that cycloheximide confers protection from doxorubicin cytotoxicity by a step which occurs following the stabilization of DNA-topoisomerase II complexes.
Bonner
J A
JA
University of Michigan Hospital, Department of Radiation Oncology, Ann Arbor 48109.
Lawrence
T S
TS
D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003513:Cycloheximide / Q000494:pharmacology*; D004250:DNA Topoisomerases, Type II / Q000096:biosynthesis; D004317:Doxorubicin / Q000037:antagonists & inhibitors* / Q000633:toxicity; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology
D011500:Protein Synthesis Inhibitors; D004317:Doxorubicin; D003513:Cycloheximide; D004250:DNA Topoisomerases, Type II