Protective effects of melatonin in reducing oxidative stress and in preserving the fluidity of biological membranes: a review

Abstract

Free radicals generated within subcellular compartments damage macromolecules which lead to severe structural changes and functional alterations of cellular organelles. A manifestation of free radical injury to biological membranes is the process of lipid peroxidation, an autooxidative chain reaction in which polyunsaturated fatty acids in the membrane are the substrate. There is considerable evidence that damage to polyunsaturated fatty acids tends to reduce membrane fluidity. However, adequate levels of fluidity are essential for the proper functioning of biological membranes. Thus, there is considerable interest in antioxidant molecules which are able to stabilize membranes because of their protective effects against lipid peroxidation. Melatonin is an indoleamine that modulates a wide variety of endocrine, neural and immune functions. Over the last two decades, intensive research has proven this molecule, as well as its metabolites, to possess substantial antioxidant activity. In addition to their ability to scavenge several reactive oxygen and nitrogen species, melatonin increases the activity of the glutathione redox enzymes, that is, glutathione peroxidase and reductase, as well as other antioxidant enzymes. These beneficial effects of melatonin are more significant because of its small molecular size and its amphipathic behaviour, which facilitates ease of melatonin penetration into every subcellular compartment. In the present work, we review the current information related to the beneficial effects of melatonin in maintaining the fluidity of biological membranes against free radical attack, and further, we discuss its implications for ageing and disease.

Effects of melatonin on the serum levels of pro-inflammatory cytokines and tissue injury after renal ischemia reperfusion in rats

“…42 Melatonin is likely to be well absorbed in humans, 43 crosses all physiological barriers easily, for example, bloodbrain barrier, membranes of cells, and organelles, additionally, has no reproducible adverse effects in humans or animals. 44 Exogenous melatonin has a short half-life (20-60 min) in human. The apparent elimination half-life of melatonin following an intravenous dose of 3 mgkg À1 (5 mgkg À1 in rats) is reported as 19.8 min in rats.…”

Melatonin: a possible link between the presence of artificial light at night and reductions in biological fitness

“…The antioxidant capacity of melatonin is derived in part because it is amphiphilic and is thus able freely to move intracellularly across membranes, including mitochondria, the organelle primarily responsible for cellular respiration and thus one of the main sites of free radical generation [62,63]. At the cellular level, endogenous melatonin has been directly linked to enhanced cell maintenance [61], mitochondrial activity [63,64] and increased antioxidant capacity of gametes in vertebrates [65,66].…”

“…(c) Melatonin, oxidative stress and immune function Melatonin's function as a free radical scavenger and potent antioxidant has been comparatively recently recognized but is now generally accepted [33,[59][60][61]. The antioxidant capacity of melatonin is derived in part because it is amphiphilic and is thus able freely to move intracellularly across membranes, including mitochondria, the organelle primarily responsible for cellular respiration and thus one of the main sites of free radical generation [62,63].…”

Melatonin reverses the enhanced oxidative damage to membrane lipids and improves skin biophysical characteristics in former-smokers – A study in postmenopausal women

“…Melatonin has been found to protect against practically all pathological processes studied to-date [1][2][3][4]. Melatonin has been documented to prevent oxidative damage in different skin components [5,6], which suggests that the human skin is a target for the protective actions of melatonin.…”