The contribution of the DNA damage response to neuronal viability.

Neurons are extremely active cells and metabolize up to 20% of the oxygen that was consumed by the organism. Despite their highly oxygenic metabolism, neuronal cells have a lower capacity to neutralize the reactive oxygen species (ROS) that they generate or to which they are exposed. High levels of ROS can lead to accumulation of damage to various cellular macromolecules. One of the cellular macromolecules highly affected by intracellular as well as extracellular insults is DNA. Neurons are also highly differentiated, postmitotic cells that cannot be replenished after disease or trauma. Since neurons are irreplaceable and should survive as long as the organism does, they need elaborate defense mechanisms to ensure their longevity. This review article mainly focuses on certain mechanisms that contribute to neuronal longevity, and concentrates on the DNA damage response in neuronal cells. The various mechanisms of DNA repair are briefly described, and focus is on those mechanisms that are activated in neuronal cells following DNA damage. Evidence is presented to show that proper DNA damage response is critically important, not just for normal neuronal development but throughout the entire life of any organism. Defective DNA damage response in older human age can generate neurodegenerative disorders such as Alzheimer's or Parkinson diseases.