Nasti Tahseen H, Timares Laura
The Department of Dermatology, University of Alabama at Birmingham School of Medicine, Birmingham, AL.
Photochem Photobiol. 2015 Jan-Feb;91(1):188-200. doi: 10.1111/php.12335. Epub 2014 Nov 7.
Skin pigmentation is due to the accumulation of two types of melanin granules in the keratinocytes. Besides being the most potent blocker of ultraviolet radiation, the role of melanin in photoprotection is complex. This is because one type of melanin called eumelanin is UV absorbent, whereas the other, pheomelanin, is photounstable and may even promote carcinogenesis. Skin hyperpigmentation may be caused by stress or exposure to sunlight, which stimulates the release of α-melanocyte stimulating hormone (α-MSH) from damaged keratinocytes. Melanocortin 1 receptor (MC1R) is a key signaling molecule on melanocytes that responds to α-MSH by inducing expression of enzymes responsible for eumelanin synthesis. Persons with red hair have mutations in the MC1R causing its inactivation; this leads to a paucity of eumelanin production and makes red-heads more susceptible to skin cancer. Apart from its effects on melanin production, the α-MSH/MC1R signaling is also a potent anti-inflammatory pathway and has been shown to promote antimelanoma immunity. This review will focus on the role of MC1R in terms of its regulation of melanogenesis and influence on the immune system with respect to skin cancer susceptibility.
皮肤色素沉着是由于角质形成细胞中两种黑色素颗粒的积累所致。黑色素除了是最有效的紫外线辐射阻滞剂外,其在光保护中的作用很复杂。这是因为一种名为真黑素的黑色素具有紫外线吸收能力,而另一种名为褐黑素的黑色素则对光不稳定,甚至可能促进癌症发生。皮肤色素沉着过度可能由压力或阳光照射引起,这会刺激受损角质形成细胞释放α-黑素细胞刺激激素(α-MSH)。黑皮质素1受体(MC1R)是黑素细胞上的关键信号分子,通过诱导负责真黑素合成的酶的表达来响应α-MSH。红发人群的MC1R发生突变,导致其失活;这导致真黑素生成不足,使红发人群更容易患皮肤癌。除了对黑色素生成的影响外,α-MSH/MC1R信号通路也是一条有效的抗炎途径,并且已被证明可促进抗黑色素瘤免疫。本综述将重点关注MC1R在调节黑色素生成方面的作用以及对皮肤癌易感性方面对免疫系统的影响。