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Disorders of Pigmentation
Published in Ayşe Serap Karadağ, Lawrence Charles Parish, Jordan V. Wang, Roxburgh's Common Skin Diseases, 2022
Michael Joseph Lavery, Charles Cathcart, Hasan Aksoy
Overview: Skin color is predominantly determined by the quantity or distribution of melanin. Hyperpigmentation is typically secondary to melanin overproduction but sometimes develops due to an increase in active melanocytes. Skin color changes may also occur via different mechanisms due to medications or heavy metals. Hyperpigmentation can be localized (e.g., melasma, nevus of Ota; Figure 25.4) or generalized (e.g. Addison disease) in distribution, and circumscribed, linear, or reticulate in configuration.
An introduction to skin and skin disease
Published in Rashmi Sarkar, Anupam Das, Sumit Sethi, Concise Dermatology, 2021
Black pigment (melanin), a polymer synthesized by melanocytes, protects against solar ultraviolet radiation (UVR). Melanocytes, unlike keratinocytes, do not have desmosomes but have long, branching dendritic projections that transport the melanin they synthesize to the surrounding cells. They originate from the embryonic neural crest. Melanocytes account for 5–10% of cells in the basal layer of the epidermis. Melanin is a polymer that is synthesized from the amino acid tyrosine with the help of a copper-containing enzyme, tyrosinase. Other pigments contribute rarely (e.g. bilirubin in jaundice or pigments derived from drugs such as minocycline or chlorpromazine). Exposure to the sun accelerates melanin synthesis, which explains suntanning. Skin color is mainly due to melanin and blood. The number of melanocytes per unit of body surface area is variable, depending on the site of the body but the density of melanocytes is the same in all humans, irrespective of race. The racial differences in complexion are attributed to the distribution and size of melanosomes, which disperse melanin to the keratinocytes. Melanocytes are completely destroyed in vitiligo. In albinism, melanin synthesis is defective. Localized increase in the synthesis of melanin leads to the development of freckles. Melanocytes in benign proliferation are referred to as nevi, and the malignant ones are known as melanomas.
Exploring the Plant Kingdom for Sources of Skincare Cosmeceuticals
Published in Mahendra Rai, Shandesh Bhattarai, Chistiane M. Feitosa, Wild Plants, 2020
Mayuri Napagoda, Sanjeeva Witharana
Skin color is primarily determined by the amount of melanin present in the skin. Melanin is a pigment produced by melanocytes through a process known as melanogenesis, from which the amino acid L-tyrosine gets converted by the enzyme tyrosinase into dopaquinone (Cooksey et al. 1997). Although melanogenesis and skin pigmentation are considered as natural photoprotective approaches in response to UV-induced skin photocarcinogenesis, the increased melanin synthesis and accumulation of these pigments give rise to many aesthetic and dermatological problems, such as melasma, periorbital hyperpigmentation, freckles, or lentigines (Smit et al. 2009, Zolghadri et al. 2019). Pigmentation is either dependent on the number, size, composition, and distribution of melanocytes, or activity of melanogenic enzymes. Furthermore, cutaneous pigmentation is resulted from melanin synthesis by melanocytes and transfer of melanosome to keratinocytes (Lin et al. 2008).
Antibacterial, Antioxidant and Melanogenesis Inhibitory Activity of Auraptene, a Coumarin from Ferula szowitsiana Root
Published in Nutrition and Cancer, 2022
Ensiyeh Charmforoshan, Ehsan Karimi, Ehsan Oskoueian, Mehrdad Iranshahi
The melanin production process (melanogenesis) takes place in cells known as melanocytes. Melanin production is necessary for skin pigmentation against UV irradiation. On the other hand, the increased production of melanin might cause several skin disorders including lentigines, nevus, freckles, melisma, and age spots. Kojic acid, linoleic acid, arbutin are tyrosinase inhibitors and used for the treatment of hyperpigmentation. Generally, the skin-whitening agents are tyrosinase inhibitors possessing toxicity against melanocytes and indicated adverse side effects. Thus, the development of natural tyrosinase inhibitors with low toxicity is necessary (28). In the present experiment, auraptene isolated from Ferula szowitsiana root possessed high inhibitory activity against tyrosinase enzyme with the IC50 values of 29.7 μg/mL however this value was lower than that of kojic acid as a reference standard with a respective IC50 value of 14.7 μg/mL (Figure 5).
Dispelling myths about sunscreen
Published in Journal of Dermatological Treatment, 2022
Sabrina Lichon Bennett, Amor Khachemoune
Tanning salons often will state that indoor tanning helps promote a protective baseline tan. However, a baseline tan obtained at a tanning salon is similar to applying sunscreen with SPF3-4, well below the recommended SPF30 (22). Additionally, tanning is the stress response from the skin to UV-induced DNA damage. When p53, a tumor suppressor protein, recognizes this DNA damage, it simulates production of pro-opiomelanocortin which in turn upregulates release of melanocyte-stimulating hormone (MSH), a pro-pigmentation hormone. This results in increased production of melanin and visible tanning. The same UV-induced DNA damage that leads to tanning can also lead to skin cancer over time (23). Thus, there is no such thing as a safe tan, and we strongly recommend against any type of tanning bed use.
A promising and effective platform for delivering hydrophilic depigmenting agents in the treatment of cutaneous hyperpigmentation: kojic acid nanostructured lipid carrier
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2021
Khadijeh Khezri, Majid Saeedi, Katayoun Morteza-Semnani, Jafar Akbari, Akbar Hedayatizadeh-Omran
Skin melanin is a biological pigment, which is produced by melanocytes. Melanin is a main factor in determining skin colour which protects human skin from the hazardous effects of ultraviolet (UV) sun radiation. Over synthesis of melanin is called hyperpigmentation [1]. Treatment of hyperpigmentation has always been challenging and discouraging for most people, especially women [2]. Kojic acid (KA) is a natural bleaching agent and a well-known tyrosinase inhibitor with hydrophilic character which is used to treat hyperpigmentation. KA inactivates the tyrosinase enzyme and suppresses the tautomerization of dopachrome by chelating copper atoms. It is synthesized by several fungal species such as the Aspergillus and Penicillum [3]. Despite the unique properties of KA and its derivatives, their use is very limited in the cosmetic industries. KA is a hydrophilic ingredient due to the presence of two hydroxyl functional groups in its chemical structure and because of its hydrophilic nature. It has inadequate absorption from the skin [4].