Vanadate-induced activation of activator protein-1: role of reactive oxygen species

M. Ding et al., Vanadate-induced activation of activator protein-1: role of reactive oxygen species, CARCINOGENE, 20(4), 1999, pp. 663-668
Citations number
Categorie Soggetti
Onconogenesis & Cancer Research
Journal title
ISSN journal
0143-3334 → ACNP
Year of publication
663 - 668
SICI code
The present study was undertaken to test the hypothesis that the toxicity a nd carcinogenicity of vanadium might arise from elevation of reactive oxyge n species leading to activation of the transcription factor activator prote in-1 (AP-1), The AP-1 transactivation response has been implicated as causa l in transformation responses to phorbol esters and growth factors. To inve stigate the possible activity of vanadium in the activation of AP-1, we tre ated mouse epidermal JB6 P+ cells stably transfected with an AP-1 luciferas e reporter plasmid with various concentrations of vanadate, This resulted i n concentration-dependent transactivation of AP-1, Superoxide dismutase (SO D) and catalase inhibited AP-1 activation induced by vanadate, indicating t he involvement of superoxide anion radical (O-2(-.)), hydroxyl radical (. O H) and/or H2O2 in the mechanism of vanadate-induced AP-1 activation. Howeve r, sodium formate, a specific .OH scavenger, did not alter vanadate-induced AP-1 activation, suggesting a minimal role for the . OH radical. NADPH enh anced AP-1 activation by increasing vanadate-mediated generation of O-2(-.) . N-acetylcysteine, a thiol-containing antioxidant, decreased activation, f urther showing that vanadate-induced AP-1 activation involved redox reactio ns. Calphostin C, a specific inhibitor of protein kinase C (PKC), inhibited activation of AP-1, demonstrating that PKC is involved in the cell signal cascades leading to vanadate-induced AP-1 activation. Electron spin resonan ce (ESR) measurements show that JB6 P+ cells are able to reduce vanadate to generate vanadium(IV) in the presence of NADPH, Molecular oxygen was consu med during the vanadate reduction process to generate O-2(-.) as measured b y ESR spin trapping using 5,5-dimethyl-L-pyrroline N-oxide as the spin trap ping agent. SOD inhibited the ESR spin adduct signal, further demonstrating the generation of O-2(-.) in the cellular reduction of vanadate, These res ults provide support for a model in which vanadium, like other classes of t umor promoters, transactivates AP-l-dependent gene expression. In the case of vanadium, AP-1 transactivation is dependent on the generation of O-2(-.) and H2O2, but not . OH.