Toxicology in Vitro
Volume 20, Issue 6 , September 2006, Pages 851-857
.
The role of iron in reactive oxygen species generation from diesel
exhaust particles

Sungjo Parka, Haeyun Namb, Namhyun Chungc, Jung-Duck Parkd and Young
Limb, ,

aDepartment of Biochemistry and Molecular Biology, Mayo Clinic and
Foundation, Rochester, MN 55905, USA
bDepartment of Occupational and Environmental Medicine, St. Mary's
Hospital, The Catholic University of Korea, Seoul 150-713, South Korea
cCollege of Life and Environmental Sciences, Korea University, Seoul
136-701, South Korea
dCollege of Medicine, Chung-Ang University, Seoul 156-756, South Korea

Received 20 June 2005;  accepted 30 December 2005.  Available online 13
February 2006.

Abstract
Diesel exhaust particles (DEP) are known to produce reactive oxygen
species (ROS), which induce oxidative stress and inflammation in the
lung and respiratory tract. DEP are composed of polycyclic aromatic
hydrocarbons (PAH) and their derivatives, redox active semi-quinones,
and trace amounts of heavy metals. ROS production was measured by
thiobarbituric acid-reactive substances of deoxyribose (TBARS)
formation from DEP samples obtained from Korea (DEP-KO), and the
Standard Reference Material (SRM) 2975 to explore the role of
transition metals. Both DEP-KO and SRM2975 had similar amounts of
transition metals, whereas DEP-KO contained more iron, but less copper
and zinc, than SRM2975. The water-soluble fraction from SRM2975, but
not that from DEP-KO, had a broad absorption in the visible region, but
not from DEP-KO, obscuring an accurate absorption measurement of TBARS.
Fluorescence measurements of TBARS generation in a water-soluble
extract showed that SRM2975 produces more TBARS, but the addition of
hydrogen peroxide (H2O2) generated more TBARS in DEP-KO than in
SRM2975, consistent with the higher amounts of iron in DEP-KO. The
incubation of DEP with iron chelators inhibited the production of
TBARS. Finally, a novel use of the fluorogenic spin trap probe, proxyl
fluorescamine, enabled the detection of the ROS production from both
DEP-KO and SRM2975. Our findings suggested that careful consideration
is needed to measure TBARS production in DEP, and that iron in DEP
seems to be more important than other transition metals in H2O2-induced
ROS generation.

Keywords: ROS; Iron; DEP; TBARS; Hydrogen peroxide

Abbreviations: DEP, diesel exhaust particles; DMSO, methyl sulfoxide;
DPTA, diethylenetriaminepentaacetic acid; Proxyl, fluorescamine
5-(2-carboxyphenyl)-5-hydroxyl-1-((2,2,5,5-tetramethyl-1-oxypyrrolidin-3-yl)methyl)3-phenyl-2-pyrrolin-4-one;
SOD, superoxide dismutase; SRM, Standard Reference Material; TBARS,
thiobarbituric acid-reactive substances of deoxyribose; ROS, reactive
oxygen species; PAH, polycyclic aromatic hydrocarbons; DEP-KO, DEP
samples obtained from Korea; H2O2, hydrogen peroxide; XPS, X-ray
photoelectron spectroscopy; ESR, electron spin resonance

Corresponding author. Tel.: +82 2 3779 1401; fax: +82 2 782 6017.

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