FIG. 5.

Some consequences of elevated ROS and RNS. Reactive oxygen species (ROS) leaked from mitochondria (e.g., O₂^−•) interact with nitric oxide (NO) produced by nitric oxide synthase (NOS) to produce reactive nitrogen species such as ONOO⁻, which covalently modify proteins. O₂^−• can also directly oxidize proteins, lipids, and carbohydrates. O₂^−• may also be dismutated to H₂O₂ by superoxide dismutase (SOD) enzymes in an attempt to mitigate O₂^−• induced damage. However, hydrogen peroxide (H₂O₂) in the presence of Fe²⁺ or Cu⁺ undergoes Fenton chemistry to produce the reactive ROS ^•OH and ⁻OH, which also cause protein, nucleic acid, and carbohydrate oxidation. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/ars