Biomedical Engineering Reference
In-Depth Information
C.
Lipid Peroxidation Products
There is increasing evidence that aldehydes, generated endogenously during
the process of lipid peroxidation, are involved in many of the pathophysio-
logical effects associated with oxidative stress in cells and tissues. Compared
with free radicals, lipid peroxidation aldehydes are generally stable, can dif-
fuse within, or even escape from the cell and attack targets far from the site
of the original free radical event. In addition to their cytotoxic properties,
lipid peroxides are increasingly recognized as being important in signal
transduction for a number of
important events in the inflammatory
response.
Isoprostanes are products of non-enzymatic lipid peroxidation and
have therefore been used as markers of oxidative stress. The isoprostanes
are ROS catalyzed isomers of arachidonic acid and are stable lipid peroxida-
tion products, which circulate in plasma and are excreted in the urine (36).
The levels of 8-iso-prostglandin F
2
a
(8-isoprostane) in EBC are elevated in
healthy smokers and more markedly in patients with COPD reflecting the
degree of oxidative stress (25,37). We have recently shown that plasma
and BALF levels of 8-isoprostanes were increased in chronic smokers and
patients with stable COPD than in healthy, age-matched non-smoking sub-
jects (Fig. 10). The plasma levels of F
2
-isoprostanes were even higher in
patients with acute exacerbations of COPD, than in patients with stable
COPD, indicating that increased oxidative stress occurs in exacerbations.
Furthermore, the increased levels of these markers of lipid peroxidation
products have been correlated with airway obstruction. Urinary levels of
Figure 10
Plasma and BALF levels of F
2
-isoprostanes in smokers with and without
COPD measured by gas chromatography
=
negative ion chemical ionization mass
spectrometry with an internal standard. Each bar is mean
SE of 12-18 subjects
=
patients.
p
<
0.05,
p
<
0.01;
p
<
0.001.
