Radiation protection and radiation recovery with essential metalloelement chelates

Understanding essential metalloelement metabolism and its role in tissue maintenance and function, as well as the roles of essential metalloelement-dependent enzymes in responding to injury, offer a new approach to decreasing and/or treating radiation injury. This review presents the roles of some essential metalloelement-dependent enzymes in tissue maintenance and function, and their responses to radiation injury in accounting for radiation protection and recovery effects observed for nontoxic doses of essential metalloelement compounds. Effects of biochemicals including water undergoing bond radiolysis and the effects of free radicals derived from diatomic oxygen account for the acute and chronic aspects of radiation injury. Recognized biochemical roles of essential metalloelement-dependent enzymes and the observed pharmacological effects of small-molecular mass chelates predict the therapeutic usefulness of essential metalloelement complexes in decreasing and/or treatment of radiation injury. Copper chelates have radiation protection and radiation recovery activities and cause rapid recovery of immunocompetency and recovery from radiation-induced histopathology. Mice treated with Cu(II)2(3,5-diisopropylsalicylate)4[Cu (II)2(3,5-DIPS)4] had increased survival and corresponding increases in numbers of myeloid and multipotential progenitor cells early after irradiation and earlier recovery of immune reactivity. Examination of radiation-induced histopathology in spleen, bone marrow, thymus, and small intestine also revealed Cu(II)2(3,5-DIPS)4-mediated rapid recovery of radiation-induced histopathology. Most recently, Fe, Mn, and Zn complexes have also been found to prevent death in lethally irradiated mice. These pharmacological effects of essential metalloelement chelates can be understood as due to facilitation of de novo synthesis of essential metalloelement-dependent enzymes which have roles in preventing the accumulation of pathological concentrations of oxygen radicals or repairing biochemical damage caused by radiation-induced bond homolysis. Essential metalloelement chelates offer a physiological approach to prevention and/or treatment of radiation injury.