melatonin
Melatonin, a ubiquitous methoxyindole, is produced by and metabolized in the skin. Melatonin affects skin functions and structures through actions mediated by cell-surface and putative-nuclear receptors expressed in skin cells. Melatonin has both receptor-dependent and receptor-independent effects that protect against oxidative stress and can attenuate ultraviolet radiation-induced damage.
The widespread expression and pleiotropic activity of the cutaneous melatoninergic system provides for a high level of cell-specific selectivity. Moreover, intra-, auto- and para-crine mechanisms equip this system with exquisite functional selectivity.
The properties of endogenous melatonin suggest that this molecule is an important effector of stress responses in the skin. Melatonin actions may counteract or buffer both environmental and endogenous stressors to maintain skin integrity.
Antioxidant effects of melatonin
The onset of lipid peroxidation within cellular membranes is associated with changes in their physicochemical properties and with the impairment of protein functions located in the membrane environment.
Melatonin has effects on biological membranes, changes in fluidity, fatty acid composition and lipid-protein modifications during the lipid peroxidation process of photoreceptor membranes and modulation of gene expression by the hormone and its preventive effects on adriamycin-induced lipid peroxidation in rat liver.
Simple model systems have often been employed to measure the activity of antioxidants. Although such studies are important and essential to understand the mechanisms and kinetics of antioxidant action, it should be noted that the results of simple in vitro model experiments cannot be directly extrapolated to in vivo systems.
For example, the antioxidant capacity of melatonin, one of the important physiological lipophilic antioxidants, in solution of pure triglycerides enriched in omega-3 polyunsaturated fatty acids is considerably different from that in subcellular membranes.
References
Catalá A.The ability of melatonin to counteract lipid peroxidation in biological membranes.Curr Mol Med. 2007 Nov;7(7):638-49. PMID: #18045142#
Slominski A, Tobin DJ, Zmijewski MA, Wortsman J, Paus R. Melatonin in the skin: synthesis, metabolism and functions. Trends Endocrinol Metab. 2008 Jan-Feb;19(1):17-24. PMID: #18155917#