Oxidative stress biomarkers in human health and disease

During the last 2 decades, oxidative stress has become increasingly important as a factor involved in the production mechanisms of numerous human diseases. There are many conditions capable of causing an unbalance between the generation of reactive species and the antioxidant activity in favor of the former (redox unbalance). This unbalance can be either due to a greater production of reactive oxygen, nitrogen, or sulfur species through enzymatic or nonenzymatic processes, to a decreased antioxidant potential, or both causes. Depending on the magnitude of the changes, a state can be found where the antioxidant defenses can abrogate the oxidative challenges, thus recovering the normal balance. However, further changes in the steady state can overwhelm the responsiveness of this defense with the result of reactive species attacks to biomolecules. This biochemical injury will cause structural and functional damage to cells, organs, and systems. Accordingly, redox unbalance recognized by oxidative stress biomarkers has been associated with numerous diseases during the last 2 decades. These biomarkers can help assessing the relationship between the occurrence of oxidative stress and the progression of diseases, as well as the effectiveness of an intervention aimed to modulate some component of the antioxidant defense system. This chapter presents an overview of the available information about the involvement of reactive oxygen and nitrogen species in cellular health and disease processes. In addition, the role of biomarkers as therapeutic targets of diseases is also analyzed.