Melatonin and skin pigmentation
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Melatonin and Skin Pigmentation: Mechanisms and Effects
Melatonin’s Role in Skin Pigmentation Regulation
Melatonin, a hormone best known for regulating circadian rhythms, also plays a significant role in skin pigmentation. In lower vertebrates like amphibians, melatonin is a key regulator of skin color, driving pigment aggregation and skin lightening, especially in response to the light/dark cycle. This process is mediated by melatonin receptors in skin pigment cells and is closely tied to circadian gene expression and environmental light cues Bertolesi2024Bertolesi2020. In these species, melatonin release at night leads to lighter skin, while disruption of circadian rhythms or continuous melatonin exposure can inhibit melanin synthesis Bertolesi2024Bertolesi2020.
Melatonin’s Effects on Human Skin Pigmentation
In humans, the effects of melatonin on skin pigmentation are more complex and less clearly defined. Some studies suggest that melatonin and its metabolites can inhibit melanin production by reducing the activity of tyrosinase, a key enzyme in melanogenesis, and by decreasing melanocyte proliferation through activation of melatonin membrane receptors (MT1, MT2) Sevilla2022Yang2023. Melatonin also appears to reduce the secretion of paracrine factors from keratinocytes that promote melanogenesis, further decreasing melanin synthesis in pigment cells .
However, other research indicates that melatonin’s effects may be dose-dependent and context-specific. For example, in long-term organ-cultured human eyelid skin, melatonin at certain concentrations increased melanin content and melanocyte activity, even though it inhibited tyrosinase activity. This suggests that melatonin can sometimes stimulate melanogenesis and melanocyte proliferation in a tyrosinase-independent manner, particularly in specific skin regions or under certain conditions .
Melatonin and UV-Induced Pigmentation
Melatonin has demonstrated protective effects against UV-induced skin pigmentation and aging. It can inhibit UVB-induced melanin synthesis and skin pigmentation by downregulating the p53-TYR pathway, which is involved in both cellular senescence and melanin production. Topical melatonin application has been shown to reduce skin erythema and pigmentation in animal models exposed to UVB radiation . These findings highlight melatonin’s potential as a protective agent against photoaging and hyperpigmentation.
Melatonin’s Antioxidant and Protective Functions in Skin
Beyond its direct effects on pigmentation, melatonin acts as a powerful antioxidant in the skin. It scavenges free radicals, stimulates the production of antioxidant enzymes, promotes DNA repair, and enhances mitochondrial function in skin cells. These actions help protect melanocytes from oxidative stress and may contribute to the regulation of pigmentation, especially under conditions of environmental stress or aging Sevilla2022Slominski2018Taheri2025.
Clinical and Therapeutic Implications
While melatonin’s skin-lightening effects are well established in lower vertebrates, its impact on human skin pigmentation is still being clarified. Some clinical observations suggest that oral melatonin can lighten hyperpigmented skin in certain conditions, but not universally across all types of hyperpigmentation . The variability in response may be due to differences in skin type, underlying conditions, or the local skin environment.
Melatonin’s ability to modulate pigmentation, protect against UV damage, and support skin health makes it a promising candidate for treating pigmentation disorders and for use in anti-aging skin care Sevilla2022Yang2023Liping2023+1 MORE. However, more research is needed to fully understand its mechanisms and to translate findings from cell and animal studies into effective clinical therapies.
Conclusion
Melatonin influences skin pigmentation through multiple pathways, including direct effects on melanocytes, modulation of keratinocyte signaling, and protection against oxidative and UV-induced damage. Its effects can be inhibitory or stimulatory depending on the context, concentration, and tissue environment. While melatonin shows promise for managing pigmentation disorders and protecting skin health, further studies are needed to clarify its role in human skin and to develop targeted therapeutic applications.
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