The Injured Cell
Jeremy R. Jass in Understanding Pathology, 2020
Melanin is the dark brown or black pigment produced by the melanocytes of the skin and passed into adjacent epithelial cells. Melanin absorbs ultraviolet light and therefore protects the skin from damage. The amount of melanin produced by organelles called melanosomes is responsible for skin colour. Inflammatory skin lesions resulting in apoptosis are marked by the presence of melanophages (macrophages that have engulfed apoptotic bodies containing melanin). Regression of malignant melanoma is also associated with the presence of melanophages. ‘Melanosis coli’ in which the colonic musosal lining accumulates brown pigment is a misnomer. The pigment is related to lipfuscin and the condition results from chronic injury to the epithelium of the large bowel caused by purgative abuse.
The Challenge of Parasite Control
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2023
Replacement strategies have also been proposed or investigated. These techniques generally focus on interfering with the development and/or the reproduction of the parasite within the vector, rendering the vector refractory to infection. For example, Anopheles gambiae, carrying transgenes involved with melanization of Plasmodium have been developed in the laboratory. Melanization is a key immune defense mechanism in invertebrates in which invading pathogens are quickly encapsulated in melanin. Owing to the enhanced melanization response, transgenic mosquitoes are resistant to infection. Likewise, A. aegypti have been engineered to express RNAi molecules that target the Zika virus genome, resulting in mosquitoes refractory to this pathogen.
Cryptococcosis
Rebecca A. Cox in Immunology of the Fungal Diseases, 2020
The abilities of C. neoformans isolates to grow at 37°C and to produce melanin have also been implicated as virulence factors.35–37 Kwon-Chung et al.35 have demonstrated that only C. neoformans isolates which can grow at 37°C and produce melanin on diphenol-containing medium will kill mice. Phenoloxidase is an important enzyme in melanin synthesis, and Rhodes et al.36 have presented data which suggest the phenoloxidase activity of C. neoformans isolates, in association with the organisms’s ability to grow at 37°C, correlates with virulence. The mechanisms by which the melanin protects the organism from host defensive measures have not been defined. It is possible that melanin production has no protective advantage as far as resistance mechanisms are concerned, but rather allows the organism to proliferate more readily in certain environments. In accord with the latter hypothesis, Polacheck et al.37 have suggested there may be some correlation between phenoloxidase activity and the preferential growth of C. neoformans in the brain of the host.
Novel tyrosinase inhibitory peptide with free radical scavenging ability
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2019
Zhiwei Shen, Yujiao Wang, Zhen Guo, Tingyuan Tan, Yi Zhang
Melanin is a natural pigment present widely in living organisms. The primary role of melanin is to reduce the skin damage caused by ultraviolet (UV) radiation. On one hand, it serves as a physical barrier and absorbent filter that scatters and limits the penetration of UV radiation7. On the other hand, it also can scavenge harmful free radicals induced by the UV radiation7–9. However, excessive accumulation and overproduction of melanin can result in the development of physiological abnormalities such as pigment spots, chloasma, freckles, age spots, and even melanoma, as well as neurodegeneration-associated diseases such as the Parkinson’s disease10–12. Furthermore, overproduction of melanin in vegetables accelerates corruption, leading to the loss of nutrients and economic wastage13,14.
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].
Skin pigmentation improvement with resveratrol microemulsion gel using polyoxyethylene hydrogenated castor oil
Published in Drug Development and Industrial Pharmacy, 2023
Lu Cao, Xiaoyan Li, Jing Zhao, Qing Du, Jiening Dun
Changes in skin pigmentation are often recognized as indicators of skin exposure to damaging agents, such as those caused by air and other pollution or radiation from electronic and electrical equipment [1]. Some previous studies suggested that the increase in skin pigment is related to the increase of epidermal cytochrome caused by pigment incontinence, the increase of melanin and melanocyte levels in the basal cell layer, and the increase of melanin particles and melanophages in the superficial layer of the dermis [2]. Melanin, which is produced in epidermal melanocytes, is a light-absorbing polymer produced by oxidation catalyzed by tyrosinase. Its production process is influenced by various signaling pathways. In addition, melanin is important in protecting skin from ultraviolet (UV) radiation damage [3]. However, abnormal melanin production can lead to many skin diseases, such as melasma and freckles, caused by melanoma and pigmentation disorders [4,5]. Thus, it is of great clinical value to study and develop drugs that can inhibit the formation of melanin in treating abnormal pigmentation.
Related Knowledge Centers
- Melanocyte
- Neuromelanin
- Redox
- Amino Acid
- Tyrosine
- Cysteine
- Benzothiazine
- Parkinson's Disease
- Ultraviolet
- Melanoma