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Triggering of Suicidal Erythrocyte Death by Topotecan
Background/Aims:
The topoisomerase I inhibitor topotecan is used as treatment of various malignancies. The substance is effective by triggering tumor cell apoptosis. In analogy to apoptosis of nucleated cells, erythrocytes may enter eryptosis, a suicidal death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the outer face of the erythrocyte membrane. Signaling leading to eryptosis include Ca(2+)-entry and ceramide formation. The present study explored, whether and how topotecan induces eryptosis.
Methods:
Phosphatidylserine abundance at the erythrocyte surface was estimated from annexin V binding, cell volume from forward scatter, and ceramide abundance utilizing specific antibodies.
Results:
A 48 hours exposure of human erythrocytes to topotecan significantly increased the percentage of annexin-V-binding cells and significantly decreased forward scatter. The effect of topotecan was paralleled by a significant increase of ceramide abundance. The effect of topotecan on annexin-V-binding was significantly blunted, but not abolished by removal of extracellular Ca2+.
Conclusions:
Topotecan stimulated cell shrinkage and phospholipid scrambling of the erythrocyte cell membrane, an effect paralleled by increase of ceramide abundance and partially dependent on entry of extracellular Ca2+.
Insights
Topotecan, a cancer drug, induces eryptosis, a form of red blood cell death. This process involves cell shrinkage, membrane changes, and calcium influx, similar to programmed cell death in other cells.
Area of Science:
- Hematology
- Cell Biology
- Pharmacology
Background:
- Topotecan is a topoisomerase I inhibitor used to treat various cancers by inducing apoptosis.
- Eryptosis, or suicidal red blood cell death, shares features with apoptosis, including cell shrinkage and phosphatidylserine translocation.
- Calcium influx and ceramide formation are key signaling pathways implicated in eryptosis.
Purpose of the Study:
- To investigate whether topotecan induces eryptosis in human erythrocytes.
- To elucidate the mechanisms by which topotecan may trigger eryptosis.
Main Methods:
- Quantification of phosphatidylserine exposure using annexin V binding.
- Measurement of erythrocyte cell volume via forward scatter analysis.
- Assessment of ceramide abundance using specific antibodies.
Main Results:
- Topotecan exposure significantly increased phosphatidylserine externalization and decreased cell volume in erythrocytes.
- A significant rise in ceramide levels was observed concurrently with topotecan treatment.
- The topotecan-induced phosphatidylserine exposure was partially dependent on extracellular calcium.
Conclusions:
- Topotecan induces eryptosis, characterized by cell shrinkage and membrane scrambling in erythrocytes.
- The eryptosis-inducing effect of topotecan is associated with increased ceramide abundance.
- Extracellular calcium influx plays a partial role in topotecan-mediated eryptosis.