| dc.description | Tobacco smoke causes oxidative damage directly by the
effect of their oxidants or indirectly through the induction of
endogenously produced oxidants and/or inactivation of antioxidants.
The oxidative effect of tobacco smoke depends on many variables:
dose, time of exposure, tissue or cell type and endogenous
antioxidant status. In an attempt to simplify this complex scenario,
we examined the effect of a soluble extract of tobacco smoke on the
activity of purified antioxidant enzymes (catalase, glutathione
peroxidase and superoxide dismutase) and in human plasma. Our
results revealed that catalase and glutathione peroxidase were
inhibited with an IC50 of 18 and 80 smoker equivalents (arbitrary
units), respectively; meanwhile superoxide dismutase was not
affected. A similar effect of soluble extract of tobacco smoke was
obtained for antioxidant enzymes in human plasma, where catalase
was inhibited, while superoxide dismutase was little affected, and
glutathione peroxidase increased 20% its activity. Benzo[a]pyrene,
a well-known component of tobacco smoke, was partly responsible
for catalase inactivation. Although soluble extract of tobacco smoke
and benzo[a]pyrene both induced carbonylation of plasma proteins,
we ruled out that catalase inhibition would be caused by
carbonylation, since the inhibition was reversed by dialysis.
Considering the higher sensitivity of catalase to inhibition induced
by soluble extract of tobacco smoke and its important role in
peroxide elimination, we conceived that benzo[a]pyrene and other
compounds of tobacco smoke extract promote a transient peroxide
accumulation which could be one of the factors responsible for the
oxidative damage in respiratory tract and other tissues in smokers. | |
