MelatoninS1204

Melatonin interacts with the highly toxic hydroxyl radical with a rate constant equivalent to that of other highly efficient hydroxyl radical scavengers. Melatonin reportedly neutralizes hydrogen peroxide, singlet oxygen, peroxynitrite anion, nitric oxide and hypochlorous acid. ^[1] Melatonin is believed to scavenge the highly toxic hydroxyl radical, the peroxynitrite anion, and possibly the peroxyl radical. Melatonin reportedly scavenges the superoxide anion radical and it quenches singlet oxygen. Melatonin stimulates mRNA levels for superoxide dismutase and the activities of glutathione peroxidase, glutathione reductase and glucose-6-phosphate dehydrogenase (all of which are antioxidative enzymes), thereby increasing its antioxidative capacity. ^[2] Melatonin in cell-free systems has been shown to directly scavenge H2O2, singlet oxygen (1O2) and nitric oxide (NO*), with little or no ability to scavenge the superoxide anion radical (O2*-) in vitro. Melatonin also directly detoxifies the peroxynitrite anion (ONOO-) and/or peroxynitrous acid (ONOOH), or the activated form of this molecule, ONOOH*. Melatonin acts as a direct free radical scavenger with the ability to detoxify both reactive oxygen and reactive nitrogen species. ^[3] Melatonin inhibits cAMP accumulation in most of the cells examined, but the indole effects on other messengers have been often observed only in one type of the cells or tissue, until now. Melatonin also regulates the transcription factors, namely, phosphorylation of cAMP-responsive element binding protein and expression of c-Fos. ^[4]