ABSTRACT
References .....................................................................................................................................132
There are three types of reactive oxygen species (ROS): oxygen-containing free radicals, reactive
anions containing oxygen atoms, or molecules containing oxygen atoms that can either produce
free radicals or are chemically activated by them. Examples are hydroxyl radical (
OH), superoxide
radical ð
O
Þ, and hydrogen peroxide (H
O
). Similar to ROS, reactive nitrogen species (RNS) can be
nitrogen-containing free radicals, reactive anions containing nitrogen atoms, or molecules containing
nitrogen atoms that can either produce free radicals or are chemically activated by them. Examples of
RNS include nitric oxide (NO
) and peroxynitrite (ONOO
). Under normal conditions, an equilibrium
exists between ROS and RNS generation, and antioxidant defenses. This equilibrium can be disturbed
by a number of factors, many of which are organ, tissue, and/or cell specific. In the lung, inhaled
particles can induce an inflammatory response, a component of which is an increase in ROS and RNS
production. This increase in ROS/RNS generation can be the result of oxidants being generated from
inhaled particles, or from lung phagocytes or epithelial cells, which have been stimulated to produce
oxidants. In this review, we describe the sources and mechanisms of particle-induced oxidative stress.
One source of cellular ROS is the mitochondria. Oxidative phosphorylation is the process by which
adenosine-5
