Reactive Oxygen and Reactive Nitrogen Species in the Lung

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) have been implicated as contributing to the pathogenesis of a broad spectrum of diseases [ 1 , 2 ]. Historically, oxygen free radicals were primarily considered to be aggressive species, indeed the superoxide (O .- 2 theory of oxygen toxicity is based on this hypothesis, (reviewed in 3). There is circumstantial evidence to support this view, some of which will be reviewed elsewhere in this chapter. However, other roles for free radicals — or more appropriately ROS and RNS — have recently emerged, most notably as signal or second messenger molecules. It seems therefore that these species can have differing effects which are dependent on their levels of production and on antioxidant defences. This chapter will mainly be concerned with the deleterious consequences associated with these reactive species, particularly in the lung, with special reference to acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.