Studies of the development of the nervous system, particularly in simple organisms such as nematode worms, revealed that many nerve cells take an active role in their own death. During apoptosis a cascade of enzymes takes place, in which one activates the next like the steps in a computer program, ultimately leading to the destruction of the cell. Each step in the cascade offers targets for the development of drugs or other interventions. In addition to the cell death cascade itself, a great deal of research is directed at insults that set it off. Cells enter apoptosis when they are damaged.
Free radicals are highly reactive chemicals that are a byproduct of normal energy metabolism.
If produced in excess or insufficiently controlled, these chemicals damage critical components of nerve cells. Because nerve cells, and especially motor neurons, require so much energy to carry out their electrical and metabolic activities, they are especially vulnerable to free radical damage. Molecular genetics is contributing greatly to our understanding of ALS, and has reinforced the suspicions about a role for free radicals in the disease process. Although only about ten percent of people with ALS inherit the disease, studying those familial cases is helping scientists to understand ALS because genetics can identify the first step in the disease,a mutant gene,in these cases. SOD normally acts to safely remove free radicals.