The brown-coloured pigment melanin is present in many different species – from humans, to birds, to microbes. It is well known that melanin affords these organisms some protection from the damaging effects of UV radiation, however the latest research indicates that melanin may also be providing a defense against ionising radiation (such as x-rays and gamma rays). (more…)
Vitiligo is a common skin depigmentation disorder in which the melanocytes, the skin cells which produce melanin pigment, are progressively lost. Despite this, melanocyte stem cells, or immature melanocytes, are preserved in a special region within hair follicles called the bulge, or niche. Often these cells are able to be stimulated with narrowband ultraviolet B (NB-UVB) phototherapy to mature into fully functional melanocytes which migrate to the epidermis to replace the lost or damaged cells. Upon further exposure to UVB radiation, skin cells (keratinocytes) manufacture a hormone called alpha-melanocyte-stimulating hormone, or α-MSH. Alpha-MSH binds to receptors on the newly formed melanocytes and activates melanin production to repigment areas of skin affected by vitiligo. (more…)
Figures 1 & 2. A vitiligo patient before and after NB-UVB treatment. Images courtesy of Pearl E Grimes, MD.
Vitiligo is a common skin depigmentation disorder in which the melanocytes, the skin cells which produce melanin pigment, are progressively lost. Clinically, when vitiliginous lesions (the ‘patches’ of skin which have lost their pigment) are repeatedly exposed to an intensive dose of narrowband UVB radiation (308 or 311-313nm), it is common to see small spots, sometimes described as ‘freckles’ or ‘islands’, of repigmentation forming within the lesion. This occurs because the melanocytes producing this melanin have developed from stem cells reserved in the bulge region of the hair follicle, known as the niche. Their development is stimulated by NB-UVB and they migrate to the skin directly surrounding the hair follicle from which they were derived. As the melanocytes continue to travel through the skin and produce melanin, these ‘islands’ begin to spread and merge, eventually creating broader, but seldom perfect, repigmentation in the treated area (see Figures 1 & 2). (more…)
Melanogenesis - click to enlarge
When skin is exposed to sunlight, ultraviolet (UV) radiation stimulates the production and release of a hormone, alpha melanocyte stimulating hormone, or α-MSH. Alpha-MSH is secreted by keratinocytes, a specific type of skin cell, then binds to receptors on the surface of another type of cell, called a melanocyte. When α-MSH binds to the receptors, which are known as MC1R, it activates the melanocytes to produce the brown/black pigment melanin. The melanin is subsequently transferred back the keratinocytes, increasing the level of melanin within the epidermis, the outer layer of the skin.
Melanin is a photoprotective to skin cells (protecting them from light/UV radiation) and the greater its density in the epidermis, the more protection is given to the layers of skin below. It does this by absorbing, reflecting and refracting light (particularly UV radiation) and preventing it from penetrating to the nucleus of keratinocytes or to lower levels of the skin. Melanin is also believed to play a role in scavenging free radicals, which can injure skin cells, and in facilitating UV induced apoptosis (programmed cell death), which removes damaged cells. Thus, melanin’s protective role goes beyond providing a physical barrier. It has been suggested that the 2-3 fold melanin levels seen in darker skin types, compared to lighter skin types, convey up to 100-fold difference in sensitivity to ultraviolet radiation due to these protective functions (see Rees 2004).
Ultraviolet (UV) radiation forms part of the electromagnetic spectrum between visible light and X-rays; it is invisible to the human eye. UV light can be separated into three bands, UVA (400-320nm), UVB (320-290nm) and UVC (290-100nm). Of the UV radiation that reaches the Earth’s surface from the sun, approximately 6% is UVB and 94% UVA.
Skin maintains a curious balance with UV radiation. When UV impacts upon skin, the various wavelengths of light penetrate to different levels and thus have a number of effects.
Each cell within the body has one or more receptors; molecules on or within the cell to which other molecules, called ligands, bind. This binding causes a series of chemical reactions within the cell, called a ‘signaling pathway’. Signaling pathways are responsible for cellular responses, allowing other cells and external elements to alter how a cell functions. There are two types of ligands which bind to receptors: agonists, which then promote a response in the pathway, and antagonists, which lead to an alternate response. (more…)
Earlier today, new stats were published by Cancer Research UK highlighting that two young adult Britons are diagnosed with skin cancer every day; a rate which has tripled since the 1970s. There were several factors highlighted as contributing to this increase, but one was most clearly singled out in the release:
“using a sunbed before the age of 35 can increase your risk of melanoma by 75%”
Have you ever wondered why the palms of your hands and the soles of your feet are lighter than the rest of your skin? Or why the skin in these areas is thicker than on other parts of your body? Researchers from the department of Geriatric and Environmental Dermatology at Nagoya City University in Japan may well have found the answer.
A small, preliminary study from the University of Adelaide (UoA) has revealed that indigenous Australians could have a high rate of vitamin D deficiency.
Vitamin D, despite its name, is actually a group of pre-hormones which is needed in small quantities by the human body. It is produced naturally in the skin upon exposure to the ultraviolet B radiation (320-280nm) in sunlight and can also be acquired through diet or supplementation. Vitamin D plays a vital role in the development and maintenance of healthy bones and deficiency can lead to bone diseases such as rickets and osteomalacia. (more…)
In many societies around the world there is a strong stigma attached to vitiligo and false beliefs prevail. It is our hope that by educating people about the disorder we can begin to change the public perception. Ideally, this will bring about better understanding and greater acceptance of individuals dealing with the condition. Here we aim to debunk some of the common myths surrounding vitiligo. (more…)
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