Biomedical Engineering Reference
In-Depth Information
Figure 5
Free iron catalyzed membrane lipid peroxidation via Fenton and Haber-
Weiss reaction.
found in the gas phase. NO and O
2
-
immediately react to form highly reac-
tive peroxynitrite (ONOO
) molecule. The radicals in the tar phase of cigar-
ette smoke are organic in nature, such as long-lived semiquinone radicals,
which can react with O
2
-
to form
OH and H
2
O
2
(8). During redox cycling,
the semiquinone intermediate reduces molecular oxygen to the superoxide
anion. The cycle can be sustained by biological reducing equivalents [ascor-
bate, NAD(P) H, glutathione, etc.] which reduce the oxidized quinoid sub-
stances back to their reduced states, enabling them to produce again the
superoxide radical (Fig. 6). The aqueous phase of cigarette smoke conden-
sate may undergo redox recycling for a considerable period of time in the
epithelial lining fluid (ELF) of smokers (8). The tar phase is also an effective
metal chelator and can bind iron to produce tar-semiquinone
þ
tar-Fe
2
þ
,
which can generate H
2
O
2
continuously (8). Furthermore, since both cigar-
ette tar and lung epithelial lining fluid contain metal ions, such as iron, Fen-
ton chemistry will result in the production of the
OH which is a highly
reactive and potent ROS. Sidestream cigarette smoke contains more than
10
17
reactive organic compounds per puff, such as carbon monoxide, nico-
tine, ammonia, formaldehyde, acetaldehyde, crotonaldehyde, acrolein, N-
nitrosamines, benzo(a) pyrene, benzene, isoprene, ethane, pentane and other
genotoxic and carcinogenic organic compounds. The concentrations of these
reactive compounds present in the epithelial lining fluid (ELF) following
inhalation of cigarette smoke have been previously calculated (11) (Table 1).
