Background/Aims: The 8-aminoquinoline tafenoquine has been shown to be effective against Plasmodia, Leishmania and Trypanosoma. The substance is at least in part effective by triggering apoptosis of the parasites. Similar to apoptosis, erythrocytes may enter suicidal death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Signaling involved in the regulation of eryptosis include increase of cytosolic Ca2+ activity ([Ca2+]i), oxidative stress, ceramide, zVAD sensitive caspases, SB203580 sensitive p38 kinase, staurosporine sensitive protein kinase C as well as D4476 sensitive casein kinase. The present study explored, whether tafenoquine induces eryptosis and aimed to possibly identify cellular mechanisms involved. Methods: Flow cytometry was employed to estimate phosphatidylserine exposure at the cell surface from annexin-V-binding, cell volume from forward scatter, [Ca2+]i from Fluo3-fluorescence, ROS formation from 2′,7′-dichlorodihydrofluorescein diacetate (DCFDA) dependent fluorescence, and ceramide abundance utilizing specific antibodies. Results: A 48 hours exposure of human erythrocytes to tafenoquine (500 ng/ml) significantly increased the percentage of annexin-V-binding cells, significantly decreased forward scatter, significantly increased Fluo3-fluorescence, and significantly increased DCFDA fluorescence. Tafenoquine did not significantly modify ceramide abundance. The effect of tafenoquine on annexin-V-binding was significantly blunted but not abolished by removal of extracellular Ca2+. The effect of tafenoquine on annexin-V-binding was not significantly blunted by zVAD (10 µM), SB203580 (2 µM) or staurosporine (1 µM). The effect of tafenoquine on annexin-V-binding was significantly blunted but not abolished by D4476 (10 µM). Conclusions: Tafenoquine triggers cell shrinkage and phospholipid scrambling of the erythrocyte cell membrane, an effect at least in part due to stimulation of Ca2+ entry, oxidative stress and possibly activation of casein kinase.
Background/Aims: The phenolic abietane diterpene component of rosemary and sage, carnosic acid, may either induce or inhibit apoptosis of nucleated cells. The mechanisms involved in the effects of carnosic acid include altered mitochondrial function and gene expression. Human erythrocytes lack mitochondria and nuclei but are nevertheless able to enter suicidal death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Cellular mechanisms involved in the stimulation of eryptosis include oxidative stress, increase of cytosolic Ca2+ activity ([Ca2+]i), and ceramide formation. The present study explored, whether and how carnosic acid induces eryptosis. Methods: Phosphatidylserine exposure at the cell surface was estimated from annexin V binding, cell volume from forward scatter, [Ca2+]i from Fluo3-fluorescence, ROS formation from DCFDA dependent fluorescence and ceramide abundance utilizing specific antibodies. Results: A 48 hours exposure of human erythrocytes to carnosic acid significantly increased the percentage of annexin-V-binding cells (2.5 µg/ml), significantly decreased forward scatter (10 µg/ml), significantly increased Fluo3 fluorescence (10 µg/ml), significantly increased ceramide abundance (10 µg/ml), significantly increased hemolysis (10 µg/ml), but significantly decreased DCFDA fluorescence (10 µg/ml). The effect of carnosic acid on annexin-V-binding was significantly blunted, but not abolished by removal of extracellular Ca2+. Conclusion: Carnosic acid triggers cell shrinkage and phospholipid scrambling of the human erythrocyte cell membrane, an effect paralleled by and/or in part due to Ca2+ entry and increased ceramide abundance.
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 Ca2+-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+.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.