Cellular responses to oxidative stress

Oxygen is essential for life yet at the same time has been shown to be a harmful cause of cellular deterioration. To avoid its deleterious effects many intricate cellular mechanisms have evolved to neutralize oxygen reactive metabolites. Every mulitcellular organism needs different types of cells with different energy needs. The level of oxygen consumption and oxidative phosphorylation of each cell type and tissue correspond to its energy needs. Oxidative stress occurs when the production of reactive oxygen species (ROS), a normal product of cellular metabolism, exceeds the ability of the cell to repair the damage caused by ROS. For that purpose, cellular oxygen concentrations are maintained with a narrow nomoxic range to circumvent the risk of oxidative damage from excess O₂. High levels of ROS can lead to the accumulation of damage to various cellular macromolecules including DNA, protein and lipids. Here we provide a definition for the redox state and oxidative stress. We also describe, in brief, the most prevalent oxygen radicals and non-radicals ROS. Additionally, we depict the antioxidant defense mechanisms. Since oxidative stress is a common denominator of many neurodegenerative diseases we provide information about the vulnerability of the brain to oxidative stress and the effect of ROS on brain aging.