Visit our Expo - Redox and Inflammation signaling 2012

Session III : Protein kinase cascades as therapeutic targets Poster III, 40
Superoxide anions are involved in doxorubicin-induced ERK activation in hepatocyte
cultures
Rosaura Navarro, Idoia Busnadiego, M. Begoña Ruiz-Larrea and José Ignacio Ruiz-
Sanz
Department of Physiology, Medicine and Dentistry School, University of the Basque
Country, 48080-Bilbao, Spain. E-mail: joseignacio.ruizs@ehu.es
Doxorubicin (DOX), an antineoplastic agent widely used for the treatment of cancer, belongs
to the anthracycline family of antitumor antibiotics. DOX may undergo one-electron
reduction to the corresponding semiquinone free radical by flavin-containing reductases.
Under aerobic conditions, the semiquinone radical reacts rapidly with oxygen to generate
superoxide anion, undergoing redox-cycling. At moderate concentrations, ROS play an
important role as regulatory mediators in signaling processes. We have shown that DOX
increased phosphorylation of enzymes comprising MAP kinase cascades in primary
hepatocyte cultures, and that this action was independent of oxidant damage. In particular,
extracellular signal-regulated kinase (ERK) was phosphorylated by the drug treatment. In this
work, we have determined the possible involvement of particular free radicals in DOXinduced
ERK phosphorylation in hepatocyte cultures by using specific free radical
scavangers. The levels of ERK phosphorylation were measured by Western blot analysis with
an anti-Thr202/Tyr204-phosphorylated 44/42 MAPK antibody. Deferoxamine (iron chelator),
catalase (hydrogen peroxide removing enzyme) or alpha-tocopherol (peroxyl-radical
scavenger) did not affect DOX-increased ERK phosphorylation levels. However, the cellpermeable
superoxide dismutase mimetic MnTBAP, and the flavin-containing enzyme
inhibitor diphenyleneiodonium, reverted DOX-induced effects. These results suggest that
superoxide anions, probably generated by DOX metabolism, are involved in the effects of the
anthracycline on the MAP kinase cascade activation.
This work was supported by the Basque Government (Research Project and Predoctoral
Training Grant to R.N.) and the University of the Basque Country (UPV00081.327-E-
15294/2003).
- 226 -