Ceruloplasmin (Cp) was found to promote the oxidative damage to DNA in vitr
o, as evidenced by the formation of 8-hydroxy-2 ' -deoxyguanosine and stran
d breaks, when incubated with a cysteine metal-catalyzed oxidation system (
Cys-MCO) comprised of Fe3+, O-2, and cysteine as an electron donor. The cap
acity of Cp to enhance oxidative damage to DNA was inhibited by hydroxyl ra
dical scavengers such as sodium azide and mannitol, a metal chelator, dieth
ylenetriaminepentaacetic acid, a spin-trapping agent, 5,5-dimethyl-1-pyrrol
ine N-oxide (DMPO) and catalase. Ceruloplasmin also caused the two-fold enh
ancement of a mutation in the pUC18 lacZ ' gene in the presence of Cys-MCO
when measured as a loss of a-complementation. Incubation of Cp with Cys-MCO
resulted in an increase in the content of carbonyl groups and the signific
ant alteration of the ferroxidase activity, as well as the proteolytic susc
eptibility. The deoxyribose assay and the salicylate hydroxylation assay sh
owed that hydroxyl free radicals were generated in the reaction of Cp with
Cys-MCO. The release of a portion of Cu from Cp was observed, and conformat
ional alterations were indicated by the changes in fluorescence spectra. Ba
sed on these results, we interpret the enhancing effect of Cp on DNA damage
and mutagenicity induced by Cys-MCO as due to reactive oxygen species, pro
bably hydroxyl free radicals, formed by the reaction of free Cu2+, released
from oxidatively damaged Cp, and H2O2 produced by Cys-MCO. The release of
Cu from Cp during oxidative stress could enhance the formation of reactive
oxygen species and could also potentiate cellular damage. (C) 2001 Societe
francaise de biochimie et biologic moleculaire / Editions scientifiques et
medicales Elsevier SAS. All rights reserved.