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DNA fragmentation induced in macrophages by gliotoxin does not require protein synthesis and is preceded by raised
1Division of Cell Biology, John Curtin School of Medical Research, Australian National University, Canberra.
Abstract:
We have shown that the immunomodulating agent gliotoxin induces DNA fragmentation in macrophages characteristic of programmed cell death or apoptosis (Waring, P., Eichner, R. D., Mullbacher, A., and Sjaarda, A. (1988) J. Biol. Chem, 263, 18493-18499). In addition, morphological changes and DNA fragmentation characteristic of apoptosis are induced in 48 h concanavalin A-stimulated T blasts by gliotoxin and these changes are inhibited by Zn2+ (Waring, P., Egan, M., Braithwaite, A., Mullbacher, A., and Sjaarda, A. (1990) Int. J. Immunopharmacol., in press). We have studied the effects of actinomycin D and the protein synthesis inhibitor cycloheximide on apoptosis induced by gliotoxin in these cells, and these studies demonstrate no effect on apoptosis induced by gliotoxin. Cycloheximide and actinomycin D alone induce DNA fragmentation in these cells. Gliotoxin itself proved to be a potent inhibitor of protein synthesis. The fragmentation caused by cycloheximide correlated with the extent of protein synthesis inhibition. The toxin ricin also induced DNA fragmentation in T blasts characteristic of apoptosis. These results indicate that protein synthesis is not required for induction of apoptosis in macrophages or T blasts by gliotoxin. Gliotoxin caused elevated levels of inositol triphosphate in treated macrophages which may be related to mobilization of Ca2+ levels during apoptosis.
Insights
The immunomodulating agent gliotoxin induces apoptosis, or programmed cell death, in macrophages and T blasts. Protein synthesis is not required for this gliotoxin-induced apoptosis.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Gliotoxin is an immunomodulating agent with known effects on cellular processes.
- Apoptosis, or programmed cell death, is a critical cellular mechanism.
- T blasts and macrophages are key immune cells involved in cellular responses.
Purpose of the Study:
- To investigate the effects of gliotoxin on apoptosis in macrophages and T blasts.
- To determine the role of protein synthesis in gliotoxin-induced apoptosis.
- To explore potential molecular mechanisms, such as calcium ion (Ca2+) mobilization, involved in gliotoxin-induced apoptosis.
Main Methods:
- Induction of apoptosis in macrophages and T blasts using gliotoxin.
- Assessment of DNA fragmentation as a marker of apoptosis.
- Treatment with actinomycin D and cycloheximide to study the role of protein synthesis.
- Measurement of inositol triphosphate levels in macrophages.
Main Results:
- Gliotoxin induces DNA fragmentation characteristic of apoptosis in macrophages and T blasts.
- Gliotoxin-induced apoptosis in T blasts is inhibited by Zn2+.
- Protein synthesis inhibitors (actinomycin D, cycloheximide) do not affect gliotoxin-induced apoptosis.
- Gliotoxin is a potent inhibitor of protein synthesis.
- Elevated inositol triphosphate levels were observed in gliotoxin-treated macrophages.
Conclusions:
- Protein synthesis is not required for gliotoxin to induce apoptosis in macrophages and T blasts.
- Gliotoxin-induced apoptosis may involve the mobilization of Ca2+ levels, potentially mediated by elevated inositol triphosphate.
- Further research is warranted to fully elucidate the signaling pathways involved in gliotoxin-induced apoptosis.