Reactive Oxygen and Nitrogen Species: Activating Signals in Inflammation

Abstract

Reactive oxygen and nitrogen species (RONS), once viewed solely as toxic by-products of aerobic metabolism and components of leukocyte bactericidal defenses, have since gained recognition as important intra- and intercellular signalling molecules in both normal as well as pathological conditions. Reactive oxygen and nitrogen species are formed in cells during oxidant stress, in reperfusion injury, and in response to several growth factors and cytokines (120). Indeed, these species may represent a novel class of second or third messengers. Like other 2nd messenger systems (e.g. Ca2+, cAMP), reactive oxygen and nitrogen species are ideal signalling molecules. They are rapidly formed and highly labile, which may serve to restrict them to specific cellular compartments and improve target specificity while reducing unwanted, non-specific effects. Most importantly, the biochemical modifications induced by modest levels of reactive nitrogen and oxygen species are largely reversible (119).