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Toxin-induced cell lysis: protection by 3-methyladenine and cycloheximide
1Institute for Cancer Research, Norwegian Radium Hospital, Montebello, Oslo.
Abstract:
The protein toxins ricin, abrin, Shiga toxin, and diphtheria toxin were found to induce lysis of several cell lines in a manner characteristic for programmed cell death or apoptosis. The toxins induced DNA degradation, and light and electron microscopical studies revealed that lysis was preceded by reorganization of intracellular vacuoles, cell blebbing, and chromatin condensation both in Vero and in MDCK cells. Cell lysis was efficiently inhibited by cycloheximide and 3-methyladenine (3MA), a specific inhibitor of autophagy. Cycloheximide, which like 3MA inhibits autophagy, protected even when added at a time when the protein synthesis had been blocked by ricin, suggesting that the effect of cycloheximide on cell lysis is independent of its ability to inhibit protein synthesis. Also theophylline and dibutyryl-cGMP had some protective effect, whereas a number of compounds reported to protect against apoptosis in other systems were without protective effects. The data suggest that autophagy is important for the toxin-induced cell lysis.
Insights
Protein toxins like ricin induce cell death resembling apoptosis. Autophagy inhibition, not protein synthesis inhibition, protected cells, suggesting autophagy
Area of Science:
- Cell Biology
- Toxicology
- Molecular Biology
Background:
- Certain protein toxins, including ricin, abrin, Shiga toxin, and diphtheria toxin, are known to induce cell death.
- The precise mechanisms underlying toxin-induced cell death, particularly the role of specific cellular processes, require further elucidation.
Purpose of the Study:
- To investigate the mechanism of cell lysis induced by protein toxins.
- To determine the role of autophagy in toxin-induced cell death.
Main Methods:
- Exposure of Vero and MDCK cell lines to protein toxins (ricin, abrin, Shiga toxin, diphtheria toxin).
- Assessment of DNA degradation, light, and electron microscopy for cellular changes.
- Evaluation of protective effects of cycloheximide, 3-methyladenine (3MA), theophylline, and dibutyryl-cGMP on toxin-induced cell lysis.
Main Results:
- Protein toxins induced cell lysis with morphological features of apoptosis, including DNA degradation, vacuole reorganization, cell blebbing, and chromatin condensation.
- Cell lysis was significantly inhibited by cycloheximide and 3-methyladenine (3MA), a specific inhibitor of autophagy.
- Cycloheximide's protective effect was independent of protein synthesis inhibition, and other apoptosis inhibitors were ineffective.
Conclusions:
- Autophagy plays a crucial role in the cell lysis induced by protein toxins.
- The findings suggest that targeting autophagy could be a strategy to mitigate the effects of these potent toxins.