Arsenite Induces Apoptosis of Murine T Lymphocytes Through Membrane Raft-Linked Signaling for Activation of c-Jun Amino-Terminal Kinase

Because of its dual roles in acute toxicity and in therapeutic application in cancer treatment, arsenic has recently attracted a renewed attention. In this study, we report NaAsO2-induced signal cascades from the cell surface to the nucleus of murine thymic T lymphocytes that involve membrane rafts as an initial signal transducer. NaAsO2 induced apoptosis through fragmentation of DNA, activation of caspase, and reciprocal regulation of Bcl-2/Bax with the concomitant reduction of membrane potential. We demonstrated that NaAsO2-induced caspase activation is dependent on curcumin-sensitive c-Jun amino-terminal kinase and barely dependent on SB203580-sensitive p38 kinase or PD98059-sensitive extracellular signal-regulated kinase. Additionally, staurosporine, which severely inhibited the activation of mitogen-activated protein (MAP) family kinases and c-Jun, partially blocked the NaAsO2-mediated signal for poly(ADP-ribose) polymerase (PARP) degradation. Potentially as the initial cell surface event for intracellular signaling, NaAsO2 induced aggregation of GPI-anchored protein Thy-1 and superoxide production. This Thy-1 aggregation and subsequent activation of MAP family kinase and c-Jun and the degradation of PARP induced by NaAsO2 were all inhibited by DTT, suggesting the requirement of interaction between arsenic and protein sulfhydryl groups for those effects. β cyclodextrin, which sequestrates cholesterol from the membrane rafts, inhibited NaAsO2-induced activation of protein tyrosine kinases and MAP family kinases, degradation of PARP, and production of superoxide. In addition, β cyclodextrin dispersed NaAsO2-induced Thy-1 clustering. These results suggest that a membrane raft integrity-dependent cell surface event is a prerequisite for NaAsO2-induced protein tyrosine kinase/c-Jun amino-terminal kinase activation, superoxide production, and downstream caspase activation.