Biomarkers of Oxidative Damage

Overwhelming evidence indicates that oxidative stress, via the overproduction of reactive species (RS), can impact on all major classes of biochemical entities including nucleic acids, proteins, amino acids, lipids, and carbohydrates. Oxidation of these entities can result in tissue injury. Many of the resulting breakdown products (8-OHdG, protein carbonyls, 4-hydroxy-2-nonenal (4-HNE), malondialdehyde (MDA), isoprostanes (IsoPs), OxLDL, etc.) are themselves highly reactive and threaten cellular integrity and function. More importantly, some of them decompose to free radicals (FR) that can continue to propagate the vicious lipid peroxidation chain reaction. Since the oxidized end-products from oxidative stress are generally more stable than the oxidants themselves, measurement of these biomarkers often showed consistent results in determining the level of the redox status in biological samples. This chapter is a comprehensive illustration of the damage that RS are capable of doing. It addresses the pathological consequences of oxidation of most important entities in cells (nucleic acids, carbohydrates, proteins, and lipids). It presents new mechanistic insights into how oxidative damage of biomolecules occurs. In addition to the extensive examination of the specific mechanisms hypothesized for the diverse pathologies, this chapter also includes a basic review of the chemistry accounting for the generation of the oxidative end-products.