Oxidative stress: the lowest common denominator of multiple diseases.

Oxygen is essential to the human life and life of all aerobic organisms. The complete oxidation of nutrients for the biological energy supply is one of the most important prerequisites for the formation of higher life forms. However, cells that benefit from oxidative respiration also suffer from reactive oxygen species because they adapted to oxygen as an energy source. Healthy cells balance the formation and elimination of reactive oxygen species thereby creating and keeping reactive oxygen species-homeostasis. When the concentration of free radicals exceeds a critical level and homeostasis is disturbed, oxidative stress occurs leading to damage of multiple cellular molecules and compartments. Therefore, oxidative stress plays an important role in the physiology and pathology of various diseases. Often, the antioxidant protection system becomes pathologically unbalanced in the genesis of several diseases, leading to functional losses of the organism, as in the case of amyotrophic lateral sclerosis, or cells develop metabolic mechanisms to use this system as protection against external influences, such as in the case of glioblastoma cells. Either way, understanding the underlying deregulated mechanisms of the oxidative protection system would allow the development of novel treatment strategies for various diseases. Thus, regardless of the direction in which the reactive oxygen species-homeostasis disequilibrate, the focus should be on the oxidative protection system.