皮肤美白产品中的活性成分

脸部不规则的色素沉着是光老化最常见的症状之一。在各种肤色的人群中,皮肤晒黑是由UVA辐射引起的。大多数防晒产品重点防止由UVB的辐射引起的皮肤晒伤。由于UVA辐射能穿透皮肤,所以防晒产品并不能防止皮肤晒黑。指出,皮肤美白最好的方法就是避免太阳光的伤害。一个好的产品不仅能将皮肤中现有的黑色素去除掉,而且还能够抑制新的黑色素产生,并防止已产生的黑色素向黑素体迁移。重点介绍了几种皮肤美白产品中的活性成分及其功效。     

Inhibitors of Intracellular Signaling Pathways that Lead to Stimulated Epidermal Pigmentation: Perspective of Anti-Pigmenting Agents

Few anti-pigmenting agents have been designed and developed according to their known hyperpigmentation mechanisms and corresponding intracellular signaling cascades. Most anti-pigmenting agents developed so far are mechanistically involved in the interruption of constitutional melanogenic mechanisms by which skin color is maintained at a normal and unstimulated level. Thus, owing to the difficulty of confining topical application to a specific hyperpigmented skin area, potent anti-pigmenting agents capable of attenuating the natural unstimulated pigmentation process have the risk of leading to hypopigmentation. Since intracellular signaling pathways within melanocytes do not function substantially in maintaining normal skin color and are activated only by environmental stimuli such as UV radiation, specifically down-regulating the activation of melanogenesis to the constitutive level would be an appropriate strategy to develop new potent anti-pigmenting agents with a low risk of hypopigmentation. In this article, we review the hyperpigmentation mechanisms and intracellular signaling pathways that lead to the stimulation of melanogenesis. We also discuss a screening and evaluation system to select candidates for new anti-melanogenic substances by focusing on inhibitors of endothelin-1 or stem cell factor-triggered intracellular signaling cascades. From this viewpoint, we show that extracts of the herbs Withania somnifera and Melia toosendan and the natural chemicals Withaferin A and Astaxanthin are new candidates for potent anti-pigmenting substances that avoid the risk of hypopigmentation.     

Study of hyperpigmentation in human skin disorder using different electron microscopy techniques

There is a global trend of increase in the demand for three‐dimensional electron microscopy with high resolution. The ultrastructural change and related functional studies are necessary to investigate biological phenomena. In this study, currently available 3D reconstruction techniques of electron microscopes (serial block‐face scanning electron microscopy and focused ion beam—scanning electron microscopy) were used to investigate hyperpigmentary disorders in human skin. In the basal layer of the epidermis in the human skin, there are melanocytes that produce melanin and keratinocytes that act as a barrier against environmental damage. The 3D structure from serial images through scanning electron microscopy showed locations of melanosomes between melanocyte and keratinocyte in the hyperpigmentary disorder, in addition, the electron tomography showed pigment transfer through melanin instead melanosome. These results support the exocytosis‐endocytosis theory of pigment in human skin.     

Synergistic Effect of 300 μm Needle-Depth Fractional Microneedling Radiofrequency on the Treatment of Senescence-Induced Aging Hyperpigmentation of the Skin

Aging-associated dermatological pigmentary diseases are associated with accumulation of senescence cells and the disruption of basement membrane due to chronic ultraviolet radiation (UVR) exposure. Our study is on the synergistic effect of the novel 300 μm needle-depth fractional microneedling radiofrequency (FMR) treatment and conventional Q-switched ND:YAG laser on aging-associated hyperpigmentation of the skin. The prospective controlled clinical trial of 25 Asian women revealed significantly higher improvements not only on wrinkles, but also on hyperpigmentation. Additional ex vivo study revealed significant reduction of pro-melanogenic markers as well as senescent keratinocytes, while increased expression of collagen type IV on the epidermal basement membrane, after additional FMR treatment on UV-irradiated human tissues. These results demonstrate that 300 μm needle-depth FMR might effectively remove senescent keratinocytes that secrete pro-melanogenic markers, and repair disrupted basement membrane, therefore preventing constant hyperpigmentation of the aged skin.