title: Sodium orthovanadate associated with pharmacological doses of ascorbate causes an increased generation of ROS in tumor cells that inhibits proliferation and triggers apoptosis.
abstract: Pharmacological doses of ascorbate were evaluated for its ability to potentiate the toxicity of sodium orthovanadate (Na(3)VO(4)) in tumor cells. Cytotoxicity, inhibition of cell proliferation, generation of ROS and DNA fragmentation were assessed in T24 cells. Na(3)VO(4) was cytotoxic against T24 cells (EC(50)=5.8 μM at 24 h), but in the presence of ascorbate (100 μM) the EC(50) fell to 3.3 μM. Na(3)VO(4) plus ascorbate caused a strong inhibition of cell proliferation (up to 20%) and increased the generation of ROS (4-fold). Na(3)VO(4) did not directly cleave plasmid DNA, at this aspect no synergism was found occurring between Na(3)VO(4) and ascorbate once the resulting action of the combination was no greater than that of both substances administered separately. Cells from Ehrlich ascites carcinoma-bearing mice were used to determine the activity of antioxidant enzymes, the extent of the oxidative damage and the type of cell death. Na(3)VO(4) alone, or combined with ascorbate, increased catalase activity, but only Na(3)VO(4) plus ascorbate increased superoxide dismutase activity (up to 4-fold). Oxidative damage on proteins and lipids was higher due to the treatment done with Na(3)VO(4) plus ascorbate (2-3-fold). Ascorbate potentiated apoptosis in tumor cells from mice treated with Na(3)VO(4). The results indicate that pharmacological doses of ascorbate enhance the generation of ROS induced by Na(3)VO(4) in tumor cells causing inhibition of proliferation and apoptosis. Apoptosis induced by orthovanadate and ascorbate is closer related to inhibition on Bcl-xL and activation of Bax. Our data apparently rule out a mechanism of cell demise p53-dependent or related to Cdk2 impairment.
authors.affiliation: Departamento de Bioquímica, Universidade Federal de Santa Catarina, Florianópolis, Brazil.
authors.forename: Tânia Mara Fischer
authors.initials: TM
authors.lastname: Günther
authors.forename: Maicon Roberto
authors.initials: MR
authors.lastname: Kviecinski
authors.forename: Carla Cristine
authors.initials: CC
authors.lastname: Baron
authors.forename: Karina Bettega
authors.initials: KB
authors.lastname: Felipe
authors.forename: Mirelle Sifroni
authors.initials: MS
authors.lastname: Farias
authors.forename: Fabiana Ourique
authors.initials: FO
authors.lastname: da Silva
authors.forename: Nádia Cristina Falcão
authors.initials: NC
authors.lastname: Bücker
authors.forename: Claus Tröger
authors.initials: CT
authors.lastname: Pich
authors.forename: Eduardo Antonio
authors.initials: EA
authors.lastname: Ferreira
authors.forename: Danilo
authors.initials: D
authors.lastname: Wilhelm Filho
authors.forename: Julien
authors.initials: J
authors.lastname: Verrax
authors.forename: Pedro Buc
authors.initials: PB
authors.lastname: Calderon
authors.forename: Rozangela Curi
authors.initials: RC
authors.lastname: Pedrosa
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001205:Ascorbic Acid / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D004247:DNA / Q000187:drug effects; D053938:DNA Fragmentation; D004357:Drug Synergism; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010957:Plasmids / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014638:Vanadates / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein / Q000819:agonists; D051020:bcl-X Protein / Q000037:antagonists & inhibitors
chemical_list: D000970:Antineoplastic Agents; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D014638:Vanadates; D004247:DNA; D001205:Ascorbic Acid