Ultraviolet radiation and melanogenesis

Abstract

Light radiation is a part of the electromagnetic radiation, and it consists of the ultraviolet (UV) radiation, visible light, and infrared radiation. UV radiation energy is absorbed in the form of photons in biomolecules (chromophores) and induces various cellular reactions, out of which photochemical and photosensitizing are the most significant. In contact with the skin UV radiation incites protection mechanisms: the most important are stratum corneum thickening and melanin synthesis (melanogenesis). Basic role of melanin is absorption and scattering of UV rays and neutralization of free radicals. In this review physical characteristics of UV radiation, its biological effects, and relation to melanogenesis and carcinogenesis are discussed

In vitroandin vivoskin anti-aging evaluation of gel containing niosomes loaded with a semi-purified fraction containing gallic acid fromTerminalia chebulagalls

“…The formulations which can reduce skin pigmentation should have the active compounds that can limit the extent of UV penetration through the epidermal layers by reflecting, scattering or absorbing the UV rays and scavenging the reactive oxygen radicals that may lead to oxidative DNA damage (Stanojevic et al, 2004). In addition, the active compounds should inhibit tyrosinase enzyme.…”

Mechanism of skin pigmentation

“…Melanin biosynthesis is dependent on proper pH homeostasis, osmotic pressure, transport of the substrate into the melanosome lumen and other uncharacterized activities such as that controlled by the OA1 protein. Proper pH and osmotic pressure are likely to require the activity of multiple spanning membrane transport proteins (pink-eyed dilution protein, P-protein, and antigen in melanoma-1/membraneassociated transporter protein (AIM-1/MATP) that have a role in ionic regulation in the melanosomes and possibly even in the ER and the Golgi [8,15,52]. If the normal Pprotein is absent, the melanosomal structure is disrupted and tyrosinase and Trp1 are misrouted to other sites.…”

“…8) [51][52][53][54]. The first mechanism suggests that the dendrite tips of the melanocytes are phagocytosed by the keratinocyte in the presence of keratinocyte receptors (Fig.…”

“…Melanin limits the extent of UV penetration through the epidermal layers and scavenges reactive oxygen radicals that may lead to oxidative DNA damage. The extent of UV-induced DNA damage and the incidence of skin cancer are inversely correlated with the total melanin content of the skin [52]. When UV radiation reaches the skin, reflection, scattering, and absorption takes place.…”

“…UV ray absorption is increased by the content of aromatic acids, such as tyrosine, tryptophan, and phenylalanine and urocanic acid, which forms in the keratinocyte by the process of keratinisation. Urocanic acid is presence mainly in the stratum corneum and is important for skin moisture mainternance, and stimulation of stratum corneum thickening and melanin synthesis by melanocytes [52].…”