calcimycin and indirubin-3--monoxime

Cordyceps sinensis is a prized traditional Chinese medicine and its major component cordycepin is found to have anti-leukemia activities. However, its cytotoxicity in erythrocytes was unclear. To examine the effect of cordycepin on the induction of eryptosis (an apoptosis-like process in enucleated erythrocytes), flow cytometric assays based on membrane integrity and asymmetry were employed. For comparison, analyses were performed in parallel with two other anti-leukemia agents, indirubin 3'-monoxime (IDM) and As2O3. We found that at the IC50 against leukemia HL-60, cordycepin elicited eryptosis while IDM and As2O3 showed no erythrotoxicity in mouse erythrocytes. Mechanistically, cordycepin increased the [Ca2+]i and activated mu-calpain protease in a dose-dependent manner. Yet, no caspase-3 activation was observed in the cordycepin-treated erythrocytes. When extracellular Ca2+ was depleted, both the cordycepin-induced eryptosis and mu-calpain cleavage were suppressed. Our study therefore demonstrated for the first time that cordycepin induces eryptosis through a calcium-dependent pathway in the absence of mitochondria and caspase-3 activation.

Topics: Animals; Antineoplastic Agents; Apoptosis; Arsenic Trioxide; Arsenicals; Blotting, Western; Calcimycin; Calcium; Caspase 3; Cell Line, Tumor; Cell Survival; Deoxyadenosines; Dose-Response Relationship, Drug; Erythrocytes; Flow Cytometry; Hemolysis; HL-60 Cells; Humans; Indoles; Intracellular Fluid; Ionophores; Mice; Mice, Inbred BALB C; Oxides; Oximes