Menadione Biphasically Controls JNK-Linked Cell Death in Leukemia Jurkat T Cells

Abstract

Signals for cell-death induction by menadione were studied in Jurkat T cells. Low concentrations of menadione (10-20 μM) and H₂O₂ (10-50 μM) induced cell death accompanying low (menadione: <5%) or moderate (H₂O₂: 10-15%) levels of DNA fragmentation in Jurkat cells. These concentrations of menadione (10 μM) and H₂O₂ also caused membrane (necrotic) cell death at unproportionally high (80%) and proportional (10-30%) levels, respectively. Higher concentrations (100-5,000 μM) of H₂O₂ exclusively induced membrane cell death. Unexpectedly, 30-300 μM menadione induced ever-decreasing levels of necrotic cell death in a concentration-dependent manner. An in vitro kinase assay showed that 20-50μM, but not >100 μM, menadione induced activation of c-Jun NH₂-terminal kinase (JNK), whereas a striking activation of JNK was induced by 500-5,000 μM H₂O₂. Induction of cell death by a low concentration of menadione was partially inhibited in dominant negative JNK gene-transfected Jurkat/VPF cells. A high concentration (300 μM) of menadione was found to inhibit cell-death induction by high concentrations (200-5,000 μM) of H₂O₂. The JNK inhibitory activity of menadione was also demonstrated in a cell-free system. However, menadione did not activate JNK in vitro. These results suggest that JNK is required for induction of not only apoptotic cell death, but also necrotic cell death in Jurkat T cells and that menadione biphasically controls this JNK-linked signal for inducing cell death.