Mitochondrial damage induced by conditions of oxidative stress

Up to 2% of the oxygen consumed by the mitochondrial respiratory chain unde rgoes one electron reduction, typically by the semiquinone form of coenzyme Q, to generate the superoxide radical, and subsequently other reactive oxy gen species such as hydrogen peroxide and the hydroxyl radical. Under condi tions in which mitochondrial generation of reactive oxygen species is incre ased (such as in the presence of Ca2+ ions or when the mitochondrial antiox idant defense mechanisms are compromised), these reactive oxygen species ma y lead to irreversible damage of mitochondrial DNA, membrane lipids and pro teins, resulting in mitochondrial dysfunction and ultimately cell death. Th e nature of this damage and the cellular conditions in which it occurs are discussed in this review article. (C) 1998 Elsevier Science Inc.