At. Kim et al., CHARACTERIZATION OF ANTIOXIDANT PROPERTIES OF NATURAL KILLER-ENHANCING FACTOR-B AND INDUCTION OF ITS EXPRESSION BY HYDROGEN-PEROXIDE, Toxicology and applied pharmacology, 147(1), 1997, pp. 135-142
Natural killer-enhancing factor B (NKEF-B) belongs to a highly conserv
ed family of recently discovered antioxidants. The role of NKEF-B as a
n antioxidant was demonstrated by its protection of transfected cells
to oxidative damage by hydrogen peroxide. To further characterize the
antioxidant properties of NKEF-B, we compared the sensitivity of a hum
an endothelial cell line ECV304 and its transfectant, B/1 that hyperex
presses NKEF-B, to various oxidants. In addition, we investigated the
changes in the expression of NKEF-B mRNA upon oxidative stress. We fou
nd that B/1 was significantly more resistant than the control cells to
the oxidative stresses caused by t-butyl hydroperoxide (t-BHP) and me
thyl mercury (MeHg). In contrast, there was no difference in the sensi
tivity of B/1 and the control cells to sulfhydryl reactive agents, die
thyl maleate and diamide. B/1 was also as sensitive as the control cel
ls to buthionine sulfoximine. The expression of NKEF-B mRNA was induce
d when the parental cell line ECV304 was treated with 2 mM HP. The ind
uction reached a maximum level around 2 hr and decreased to the basal
level around 4 hr. NKEF-A mRNA was not induced by HP. These results de
monstrate antioxidant activities of NKEF-B toward prooxidants such as
alkyl hydroperoxide and MeHg. Together with its antioxidant activity,
the induction of NKEF-B by HP indicates that NKEF-B is an important ox
idative stress protein providing protection against a variety of xenob
iotic toxic agents. (C) 1997 Academic Press.