Antioxidative effects of melatonin in protection against cellular damage caused by ionizing radiation

Ionizing radiation is classified as a potent carcinogen, and its injury to living cells is, to a large extent, due to oxidative stress. The molecule m ost often reported to be damaged by ionizing radiation is DNA. Hydroxyl rad icals ((OH)-O-.), considered the most damaging of oil free radicals generat ed in organisms, am often responsible for DNA damage caused by ionizing rad iation. Melatonin, N-acetyl-5-methoxytryptamine, is a well-known antioxidan t that protects DNA, lipids, and proteins from free-radical damage. The ind oleamine manifests its antioxidative properties by stimulating the activiti es of antioxidant enzymes and scavenging free radicals directly or indirect ly. Among known antioxidants, melatonin is a highly effective scavenger of (OH)-O-.. Melatonin is distributed ubiquitously in organisms and, as far as is known, in all cellular compartments, and it quickly passes through all biological membranes. The protective effects of melatonin against oxidative stress caused by ionizing radiation have been documented in in vitro and i n vivo studies in different species and in in vitro experiments that used h uman tissues, as well as when melatonin was given to humans and then tissue s collected and subjected to ionizing radiation. The radioprotective effect s of melatonin against cellular damage caused by oxidative stress and its l ow toxicity make this molecule a potential supplement in the treatment or c otreatment in situations where the effects of ionizing radiation are to be minimized.