Melatonin and human skin aging

Konrad Kleszczynski, Tobias W Fischer, Konrad Kleszczynski, Tobias W Fischer

Abstract

Like the whole organism, skin follows the process of aging during life-time. Additional to internal factors, several environmental factors, such as solar radiation, considerably contribute to this process. While fundamental mechanisms regarding skin aging are known, new aspects of anti-aging agents such as melatonin are introduced. Melatonin is a hormone produced in the glandula pinealis that follows a circadian light-dependent rhythm of secretion. It has been experimentally implicated in skin functions such as hair cycling and fur pigmentation, and melatonin receptors are expressed in many skin cell types including normal and malignant keratinocytes, melanocytes and fibroblasts. It possesses a wide range of endocrine properties as well as strong antioxidative activity. Regarding UV-induced solar damage, melatonin distinctly counteracts massive generation of reactive oxygen species, mitochondrial and DNA damage. Thus, there is considerable evidence for melatonin to be an effective anti-skin aging compound, and its various properties in this context are described in this review.

Keywords: antioxidative enzymes; apoptosis; melatonin; mitochondrial damage; oxidative stress; skin; ultraviolet radiation.

Figures

https://www.ncbi.nlm.nih.gov/pmc/articles/instance/3583885/bin/de-4-245-g1.jpg
Figure 1. Synthesis of melatonin in the skin. It is involved sequential transformation of tryptophan in a cascade of enzymatic reactions catalyzed by tryptophan hydroxylase (TPH1, TPH2), amino acid decarboxylase (AAD), arylalkylamine N-acetyltransferase (AANAT), arylamine N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT).
https://www.ncbi.nlm.nih.gov/pmc/articles/instance/3583885/bin/de-4-245-g2.jpg
Figure 2. The melatoninergic antioxidative system in human skin. Parallel to directly scavenging UVB-induced reactive oxygen species (ROS), namely hydroxyl radicals, melatonin is transformed to 2-hydroxymelatonin, 4-hydroxymelatonin and consecutively to AFMK. All metabolites are strong antioxidants themselves creating a potent antioxidative cascade that reduces lipid peroxidation, protein oxidation, mitochondrial and DNA damage. SC, stratum corneum; SL, stratum lucida; SG, stratum granulosum; SS, stratum spinosum; SB, stratum basale; BM, basement membrane

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