[Valproic acid induced intracellular GSH-redox imbalance and apoptosis of leukemic cells resistant to dexamethasone and doxorubicin].

Objective To investigate the anti-neoplastic effects of Valproic acid(VPA)on leukemic cells,especially drug-resistant lines,and to investigate whether modulation of GSH-redox status is involved in VPA-induced apoptosis.Methods After the treatment of VPA at various concentrations for indicated times,cellular proliferation of the Jurkat,CEM,HL-60,K562,K562/AO2 cells were evaluated via MTT assay;and the activities of Caspase-3,Caspase-8 and Caspase-9 were quantitatively analyzed by colorimetric assay.The morphological change and cell cycle distribution were also examined on Jurkat(Dexamethasone-resistant)and K562/AO2(Doxorubicin-resistant)cell lines.The levels of intracellular glutathione/glutathione disulfide(GSH/GSSG)and the activities of the typical antioxidant enzymes,i.e.,glutathione reductase(GSH-Rd)and glutathione peroxidase(GSH-Px),were measured on cell lysates of Jurkat and K562/AO2 cell lines prior to and after VPA treatment.Apoptosis rates of Jurkat and K562/AO2 cells treated with VPA along or in combination with N-acetyl-l-cysteine(NAC),catalase(CAT)or DL-buthionine-(S,R)-sulfoximine(BSO)were determined by Annexin V/propidium iodide(PI)staining with flow cytometry analysis.Results At concentrations comparable with that achieved at clinical settings,VPA inhibited cell proliferation,activated Caspase-3,8,and 9,and induced cell cycle arrest in Jurkat and K562/AO2.A rapid decrease in GSH-Rd and GSH-Px activities and GSH content in Jurkat and K562/AO2 were detected after VPA treatment.Co-administration of NAC or CAT attenuated VPA-induced apoptosis.Conclusion VPA inhibit cell proliferation,induce cell cycle arrest and apoptosis in drug-resistant leukemic cells.Apoptosis correlates with down-regulation of intracellular GSH and disruption of intracellular GSH-redox balance,possibly through inhibition of glutathione reductase and glutathione peroxidase.