RNA- and protein-synthesis inhibitors induce apoptosis in a midgut cell line from the spruce budworm, Choristoneura fumiferana

RNA-synthesis inhibitors actinomycin D and dichlorobenzimidazole riboside, and protein-synthesis inhibitors anisomycin and cycloheximide induced apoptosis in FPMI-CF-203 (CF-203), a continuous midgut cell line of Choristoneura fumiferana. Actinomycin D induced apoptosis in more than 90% of the CF-203 cells at a concentration as low as 0.01 μg/ml of medium. Dichlorobenzimidazole riboside, on the other hand, induced apoptosis in 99% of these cells at a concentration of 100 μg/ml or higher. A concentration of 50 μg/ml or higher of anisomycin induced apoptosis in more than 90% of these cells by 24 h after treatment. Cycloheximide was the least effective, requiring 100 and 500 μg/ml to induce apoptosis in 17 and 30% of these cells, respectively, by 24 h after treatment. The cells treated with actinomycin D showed an oligomeric ladder beginning at 6 h after treatment, whereas the cells treated with dichlorobenzimidazole riboside, anisomycin or cycloheximide showed the oligomeric ladder beginning at 12 h after treatment. Some of the CF-203 cells treated with actinomycin D or anisomycin showed the classical apoptotic morphological characteristics such as plasma membrane blebbing, nuclear fragmentation and packaging of cytoplasmic organelles and chromatin into apoptotic bodies by 8 h after treatment, and by 24 h after treatment the effects were evident in most of the cells. Thus, two different classes of chemicals that inhibit RNA synthesis and protein synthesis by different modes of action, induced apoptosis in CF-203 cells.