CYCLOHEXIMIDE CAN RESCUE HEAT-SHOCKED L-CELLS FROM DEATH BY BLOCKING STRESS-INDUCED APOPTOSIS

Cultured mouse L cells undergo apoptosis upon 1 h heat shock at 43 and 45 °C. Morphologically characteristic apoptotic cells begin to appear soon after the shock. Immunohistochemistry with anti-transglutaminase antibody shows that in most treated cells the enzyme is induced. Its activation results in the formation of highly cross-linked detergent-resistant apoptotic bodies during recovery. Cycloheximide added during hyperthermic stress inhibits the appearance of apoptotic bodies, showing that heat-shock-induced apoptosis is dependent on protein neosynthesis. The analysis of colony-forming ability of heat-shocked L cells shows a survival of 5% at 43 °C and <0.02% at 45 °C. When protein synthesis is inhibited during heat shock the fraction of surviving cells increases to 23% at 43 °C and 0.9% at 45 °C. This suggests that part of the cells that die upon heat shock are not heavily damaged and would have survived in the presence of a block in protein synthesis. © 1992.