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Apoptotic pathways depend on the target enzymatic activity and not on the triggering agent
F Luchetti1, A R Mariani, M Columbaro
1Istituto Scienze Morfologiche, University Urbino, Italy.
Abstract:
Molt-4 human leukemia cells were triggered to apoptosis by various agents with different mechanisms of action. Staurosporine, a protein kinase C (PKC) inhibitor; camptothecin, a topoisomerase I blocking drug; and tiazofurin, an inhibitor of inosine 5'-phosphate dehydrogenase (IMPDH), were used. Ultrastructural analysis showed morphologic changes characteristic of apoptosis that were very similar for all three agents. Nevertheless, DNA oligonucleosomic fragmentation was not detectable by agarose gel electrophoresis. However, a genomic DNA cleavage appeared after pulse-field gel electrophoresis (PFGE) in cells treated with these agents for 24 h. Furthermore, in situ nick translation (NT) showed a finely spotted nuclear labelling in staurosporine-treated cells and a compact fluorescence after camptothecin incubation. In tiazofurin-treated cells an intermediate pattern was found. Therefore, apoptotic agents with different mechanisms of action induced the formation of large genomic DNA fragments and very similar ultrastructural changes. Therefore, both phenomena and the closely related apoptosis progression depend on target cell machinery and not on the triggering agent.
Insights
Various agents trigger apoptosis in leukemia cells, causing similar ultrastructural changes and large genomic DNA fragments. Apoptosis progression relies on cellular machinery, not the specific triggering agent.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Apoptosis, or programmed cell death, is crucial for development and disease.
- Different agents can induce apoptosis through diverse mechanisms.
- Understanding the common pathways of apoptosis is essential.
Purpose of the Study:
- To investigate the commonalities in apoptosis induction by agents with different mechanisms.
- To analyze ultrastructural changes and DNA fragmentation patterns during apoptosis.
- To determine the role of cellular machinery versus triggering agents in apoptosis.
Main Methods:
- Treatment of Molt-4 human leukemia cells with staurosporine (PKC inhibitor), camptothecin (topoisomerase I inhibitor), and tiazofurin (IMPDH inhibitor).
- Ultrastructural analysis using electron microscopy.
- DNA fragmentation analysis via agarose gel electrophoresis and pulse-field gel electrophoresis (PFGE).
- In situ nick translation (NT) assay.
Main Results:
- All agents induced similar ultrastructural changes characteristic of apoptosis.
- Oligonucleosomal DNA fragmentation was not detected, but genomic DNA cleavage was observed via PFGE after 24h.
- In situ nick translation showed distinct nuclear labeling patterns for each agent, indicating varied DNA damage sites.
Conclusions:
- Diverse apoptotic agents induce large genomic DNA fragments and similar ultrastructural changes.
- Apoptosis progression and DNA fragmentation are dependent on the target cell's machinery, not solely on the inducing agent.
- These findings highlight conserved pathways in apoptosis regardless of the initial trigger.