Camalexin induces apoptosis in T-leukemia Jurkat cells by increased concentration of reactive oxygen species and activation of caspase-8 and caspase-9

• Published in: Journal of natural medicines 2011-07, Vol.65 (3-4), p.488-499
• Main Authors: Mezencev, Roman, Updegrove, Taylor, Kutschy, Peter, Repovská, Mária, McDonald, John F.
• Format: Article
• Language: English
• Subjects: Apoptosis - drug effects; Biomedical and Life Sciences; Biomedicine; Caspase 8 - metabolism; Caspase 9 - metabolism; Cell Cycle - drug effects; Cells, Cultured; Complementary & Alternative Medicine; Enzyme Activation - drug effects; Glutathione - metabolism; Humans; Indoles - chemistry; Indoles - pharmacology; Jurkat Cells; Leukemia, T-Cell - metabolism; Medicinal Chemistry; Membrane Potential, Mitochondrial - drug effects; Molecular Structure; Original Paper; Pharmacology/Toxicology; Pharmacy; Plant Sciences; Reactive Oxygen Species - metabolism; Superoxides - metabolism; Thiazoles - chemistry; Thiazoles - pharmacology
• ISSN: 1340-3443; 1861-0293
• DOI: 10.1007/s11418-011-0526-x

Camalexin, a major indole phytoalexin of Arabidopsis thaliana , accumulates in various cruciferous plants in response to environmental stress and reportedly displays antimicrobial activities against various plant pathogens. However, its cytotoxicity against eukaryotic cells and potential as a prospective drug for human diseases has been examined only in a limited context. Our data demonstrate the time- and concentration-dependent cytotoxicity of camalexin on human T-leukemia Jurkat cells in the micromolar range, and the lower potency of cytotoxic effects on human lymphoblasts and primary fibroblasts. Cytotoxicity of camalexin is enhanced by the glutathione-depleting agent buthionine sulfoximine and completely blocked by pan-caspase inhibitor Z-VAD-FMK. Treatment of Jurkat cells with camalexin resulted in activation of caspase-8, caspase-9, caspases-3/7, and apoptosis that was detected by the presence of a sub-G1 population of cells, externalization of phosphatidyl serine and decreased mitochondrial membrane potential. Staining with 2′,7′-dichlorodihydrofluorescein diacetate and dihydroethidium bromide displayed increased concentration of reactive oxygen species (ROS) early in camalexin-treated Jurkat cells, prior to the onset of apoptosis, while staining with MitoSOX ™ dye identified mitochondria as a source of increased ROS. Our data suggest that this phytochemical, which has a wide range of predicted pharmacological activities, induces apoptosis in Jurkat leukemia cells through increased ROS followed by dissipation of mitochondrial membrane potential and execution of caspase-9- and caspase-8-initiated apoptosis. This is, to the best of our knowledge, the first report on antileukemic activity and mode of action of this unique indole phytoalexin.