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DNA fragmentation in S49 lymphoma cells killed with glucocorticoids and other agents
Abstract:
The effects of glucocorticoids on DNA integrity in the mouse S49 lymphoma cell line were assessed. DNA cleavage at the internucleosomal regions was observed, and this response was correlated to the dose of hormone used and the time of treatment. Also, an apparent steroid specificity was observed: internucleosomal cleavage was associated only with treatment of the cells with glucocorticoids. Cells treated with dibutyryl cyclic AMP (which also causes lymphocytolysis) also exhibited DNA cleavage. However, when cells were killed with various DNA synthesis inhibitors and other lethal agents, the same DNA cleavage pattern was observed. Furthermore, new protein synthesis did not seem to be required, since cells killed with puromycin and cycloheximide also exhibited internucleosomal DNA fragmentation. Although DNA fragmentation may not be a specific early effect of glucocorticoid-mediated lymphocytolysis, it may be the final, irrevocable step in this complex process.
Insights
Glucocorticoids cause DNA fragmentation in lymphoma cells, but this DNA cleavage is not specific to these hormones and may be a final step in cell death. Keywords: glucocorticoids, DNA fragmentation, lymphoma cells, cell death.
Area of Science:
- Molecular Biology
- Cell Biology
- Endocrinology
Background:
- Glucocorticoids are known to induce apoptosis in lymphoid cells.
- The precise mechanisms underlying glucocorticoid-induced cell death are complex and not fully understood.
Purpose of the Study:
- To investigate the effects of glucocorticoids on DNA integrity in mouse S49 lymphoma cells.
- To determine if DNA cleavage is a specific marker of glucocorticoid action.
Main Methods:
- Treatment of mouse S49 lymphoma cells with varying doses and durations of glucocorticoids.
- Analysis of DNA integrity using gel electrophoresis to detect internucleosomal cleavage.
- Comparison of DNA cleavage patterns induced by glucocorticoids with those induced by other agents like dibutyryl cyclic AMP, DNA synthesis inhibitors, and protein synthesis inhibitors.
Main Results:
- Glucocorticoid treatment led to DNA cleavage at internucleosomal regions, dose- and time-dependently.
- This DNA cleavage was observed only with glucocorticoids, suggesting steroid specificity.
- Similar internucleosomal DNA fragmentation was induced by dibutyryl cyclic AMP, DNA synthesis inhibitors, and protein synthesis inhibitors (puromycin, cycloheximide).
Conclusions:
- DNA fragmentation is not a specific early event in glucocorticoid-induced lymphocytolysis.
- Internucleosomal DNA fragmentation may represent a common, final pathway in the programmed cell death of lymphoma cells, regardless of the initial trigger.
- The findings suggest that while glucocorticoids initiate cell death, the observed DNA fragmentation is a downstream event.