ABSTRACT
Reactive oxygen species (ROS) are generated from molecular oxygen and include the free radicals superoxide (*O2-), hydroxyl (*OH), and nitric oxide (NO'), as well as nonradical intermediates such as hydrogen peroxide (H2O2) and singlet oxygen ('O2). During normal cellular respiration, ROS are constantly produced at low rate, in particular by mitochondria. At these low concentrations, ROS can act as second-messengers and as mediators for cell activation (1). However, during infection or inflammation, or upon exposure to environmental stresses such as ionizing or nonionizing radiation, metals, or various toxic compounds, ROS can accumulate to deleterious levels and damage almost all cellular components (1,2). Endogenous mechanisms to detoxify the oxidants and to repair the damage caused by ROS include, among others, the heat shock/stress proteins (HSP).
