Reactive oxygen species-regulated glycogen synthase kinase-3β activation contributes to all-trans retinoic acid-induced apoptosis in granulocyte-differentiated HL60 cells

All-trans retionic acid (ATRA) treatment confers disease remission in acute promyelocytic leukemia (APL) patients by inducing granulocytic differentiation, which is followed by cell apoptosis. Although glycogen synthase kinase (GSK)-3 beta is known to be required for spontaneous cell death in neutrophils, the requirement of GSK-3 beta activation for the apoptotic effects remains unknown. This question is addressed in the present study using a model of ATRA-induced granulocytic differentiation and apoptosis in APL HL60 cells. ATRA at a therapeutic concentration (1 mu M) induced granulocytic differentiation, followed by apoptosis. ATRA treatment caused decreased Mcl-1, caspase-3 activation, and PARP cleavage following the inactivation of phosphatidylinositol 3-kinase/AKT and the activation of GSK-3 beta. Pharmacologically and genetically inhibiting GSK-3 beta effectively retarded ATRA-induced Mcl-1 degradation and apoptosis. Additional differentiation inducers, phorbol 12-myristate 13-acetate and dimethyl sulfoxide, also triggered GSK-3 beta-dependent apoptosis. Mechanistically, ATRA caused the generation of reactive oxygen species (ROS) through increased expression of NADPH oxidase subunits (p47(Phox) and p67(Phox)) to facilitate ATRA-induced GSK-3 beta activation and cell apoptosis. This study indicates that ROS initiate GSK-3 beta-dependent apoptosis in granulocyte-differentiated cells after long-term ATRA treatment. (C) 2014 Elsevier Inc. All rights reserved.