Free Radicals in Down's Syndrome, Amyotrophic lateral sclerosis & Rheumatoid Arthritis

Abstract

A free radical is an atom or group of atoms that have one or more unpaired electrons that can be considered as fragments of molecules and which are generally very reactive. Free Radicals can have positive, negative or neutral charge. They are produced continuously in cells either as accidental by-products of metabolism or deliberately during, for example, phagocytosis. The most important reactants in free radical biochemistry in aerobic cells are oxygen and its radical derivatives (superoxide and hydroxyl radical), hydrogen peroxide and transition metals. Cells have developed a comprehensive array of antioxidant defences to prevent free radical formation or limit their damaging effects. These include enzymes to decompose peroxides, proteins to sequester transition metals and a range of compounds to ‘scavenge’ free radicals. Reactive free radicals formed within cells can oxidise biomolecules and lead to cell death and tissue injury. Establishing the involvement of free radicals in the pathogenesis of a disease is extremely difficult due to the short lifetimes of these species. We describe the role of free radicals in Down's syndrome, Amyotrophic lateral sclerosis and Rheumatoid arthritis.