Abstract
Uncontrolled exposure to radiation from possible nuclear battlefields, outer space travel or accidents at nuclear power plants presents the greatest threat and challenge to the civilized world today. The consequences of ionizing radiation, either from intentional or unintentional sources, on cells and tissues are complex phenomena. Death from radiation exposure is the result of sequences of events which occur within a fraction of a second to several weeks. One of the most challenging tasks of radiobiology today is the development of pharmacological agents that can protect, repair and regenerate the early damage produced in cells and tissues by ionizing radiation. Protection depends on the ability of chemical agents to reduce the intracellular concentration of free radicals and reactive oxygen species that are produced within the first millisecond after irradiation. The first-generation chemical agents used as radioprotectants are compounds with antioxidant and scavenging potential. Various novel compounds are currently under clinical investigation as radioprotectants that can accelerate recovery of tissue stem cells and their precursors after radiation exposure. Current treatment strategies also include the use of immunomodulators and natural products with free radical-scavenging capability and the ability to induce bone morrow recovery.