[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-acety-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.


CONCLUSIONS
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.
Liu
Heng
H
Department of Pediatric Hematology and Oncology, West China Second Hospital, Sichuan University, Chengdu 610041, China.
Fu
Ren-Yi
RY
Liao
Qing-Kui
QK
Li
Feng-Yi
FY
Zhu
Yi-Ping
YP
Gao
Ju
J
Mao
Yong-Qiu
YQ
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D003907:Dexamethasone / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D005978:Glutathione / Q000378:metabolism*; D005979:Glutathione Peroxidase / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D019169:Jurkat Cells; D020014:K562 Cells; D014635:Valproic Acid / Q000494:pharmacology*
D000970:Antineoplastic Agents; D014635:Valproic Acid; D003907:Dexamethasone; D004317:Doxorubicin; D005979:Glutathione Peroxidase; D005980:Glutathione Reductase; D005978:Glutathione