Hydrolyzed Conchiolin Protein (HCP) Extracted from Pearls Antagonizes both ET-1 and α-MSH for Skin Whitening

Pearl powder is a famous traditional Chinese medicine that has a long history in treating palpitations, insomnia, convulsions, epilepsy, ulcers, and skin lightining. Recently, several studies have demonstrated the effects of pearl extracts on protection of ultraviolet A (UVA) induced irritation on human skin fibroblasts and inhibition of melanin genesis on B16F10 mouse melanoma cells. To further explore the effect we focused on the whitening efficacy of pearl hydrolyzed conchiolin protein (HCP) on human melanoma MNT-1 cells under the irritation of alpha-melanocyte-stimulating hormone (α-MSH) or endothelin 1 (ET-1) to evaluate the intracellular tyrosinase and melanin contents, as well as the expression levels of tyrosinase (TYR), tyrosinase related protein 1 (TRP-1), and dopachrome tautomerase (DCT) genes and related proteins. We found that HCP could decrease the intracellular melanin content by reducing the activity of intracellular tyrosinase and inhibiting the expression of TYR, TRP-1, DCT genes and proteins. At the same time, the effect of HCP on melanosome transfer effect was also investigated in the co-culture system of immortalized human keratinocyte HaCaT cells with MNT-1. The result indicated that HCP could promote the transfer of melanosomes in MNT-1 melanocytes to HaCaT cells, which might accelerate the skin whitening process by quickly transferring and metabolizing melanosomes during keratinocyte differentiation. Further study is needed to explore the mechanism of melanosome transfer with depigmentation.

Alpha-Synuclein and Its Role in Melanocytes

Pigmentation is an important process in skin physiology and skin diseases and presumably also plays a role in Parkinson’s disease (PD). In PD, alpha-Synuclein (aSyn) has been shown to be involved in the pigmentation of neurons. The presynaptic protein is intensively investigated for its pathological role in PD, but its physiological function remains unknown. We hypothesized that aSyn is both involved in melanocytic differentiation and melanosome trafficking processes. We detected a strong expression of aSyn in human epidermal melanocytes (NHEMs) and observed its regulation in melanocytic differentiation via the microphthalmia-associated transcription factor (MITF), a central regulator of differentiation. Moreover, we investigated its role in pigmentation by performing siRNA experiments but found no effect on the total melanin content. We discovered a localization of aSyn to melanosomes, and further analysis of aSyn knockdown revealed an important role in melanocytic morphology and a reduction in melanosome release. Additionally, we found a reduction of transferred melanosomes in co-culture experiments of melanocytes and keratinocytes but no complete inhibition of melanosome transmission. In summary, this study highlights a novel physiological role of aSyn in melanocytic morphology and its so far unknown function in the pigment secretion in melanocytes.

Transcriptomic and Functional Evidence Show Similarities between Human Amniotic Epithelial Stem Cells and Keratinocytes

Amniotic epithelial stem cells (AESCs) are considered as potential alternatives to keratinocytes (KCs) in tissue-engineered skin substitutes used for treating skin damage. However, their clinical application is limited since similarities and distinctions between AESCs and KCs remain unclear. Herein, a transcriptomics analysis and functional evaluation were used to understand the commonalities and differences between AESCs and KCs. RNA-sequencing revealed that AESCs are involved in multiple epidermis-associated biological processes shared by KCs and show more similarity to early stage immature KCs than to adult KCs. However, AESCs were observed to be heterogeneous, and some possessed hybrid mesenchymal and epithelial features distinct from KCs. A functional evaluation revealed that AESCs can phagocytose melanosomes transported by melanocytes in both 2D and 3D co-culture systems similar to KCs, which may help reconstitute pigmented skin. The overexpression of TP63 and activation of NOTCH signaling could promote AESC stemness and improve their differentiation features, respectively, bridging the gap between AESCs and KCs. These changes induced the convergence of AESC cell fate with KCs. In future, modified reprogramming strategies, such as the use of small molecules, may facilitate the further modulation human AESCs for use in skin regeneration.

Induction of retinal-dependent calcium influx in human melanocytes by UVA or UVB radiation contributes to the stimulation of melanosome transfer

OBJECTIVES

The transfer of melanosomes from melanocytes to neighbouring keratinocytes is critical to protect the skin from the deleterious effects of ultraviolet A (UVA) and ultraviolet B (UVB) irradiation; however, the initial factor(s) that stimulates melanosome transfer remains unclear. In this study, we investigated the induction of retinal-dependent calcium (Ca²⁺ ) influx in melanocytes (MCs) by UVA or UVB irradiation and the effect of transient receptor potential cation channel subfamily M member 1 (TRPM1) (melastatin1)-related Ca²⁺ influx on melanosome transfer.

MATERIALS AND METHODS

Primary human epidermal MCs were exposed to physiological doses of UVB or UVA light and loaded with a calcium indicator Fluo-4 dye. The change of intracellular calcium of MCs was monitored using a two-photon confocal fluorescence microscopy. MCs were co-cultured with human epidermal keratinocytes (KCs) in the absence or presence of voriconazole (a TRPM1 blocker) or calcium chelators. MCs were also transfected with TRPM1 siRNA for silencing the expression of TRPM1 gene. The melanosome transfer in the co-cultured cells was quantitatively analysed using flow cytometry and was further confirmed by immunofluorescent double-staining. The protein levels and distributions of TRPM1, OPN3 and OPN5 in MCs were measured by Western blotting or immunofluorescent staining.

RESULTS

The retinal-dependent Ca²⁺ influx of UVA-exposed melanocytes differed greatly from that of UVB-exposed melanocytes in the timing-phase. The protein expression of TRPM1 in mono- and co-cultured MCs was dose-dependently up-regulated by UVA and UVB. TRPM1 siRNA-mediated knockdown and the blockage of TRPM1 channel using a putative antagonist (voriconazole) significantly inhibited melanosome transfer in co-cultures following UVA or UVB exposure.

CONCLUSIONS

The distinct time-phases of Ca²⁺ influx in MCs induced by UVA or UVB contribute to the consecutive stimulation of melanosome transfer, thereby providing a potent photoprotection against harmful UV radiation.

Multiepitope tissue analysis reveals SPPL3-mediated ADAM10 activation as a key step in the transformation of melanocytes

The evolution of cancer is characterized by the appearance of specific mutations, but these mutations are translated into proteins that must cooperate to induce malignant transformation. Using a systemic approach with the multiepitope ligand cartography (MELC) technology, we analyzed protein expression profiles (PEPs) in nevi and BRAF^V600E-positive superficial spreading melanomas (SSMs) from patient tissues to identify key transformation events. The PEPs in nevi and SSMs differed predominantly in the abundance of specific antigens, but the PEPs of nevi- and melanoma-associated keratinocytes gradually changed during the transformation process. A stepwise change in PEP with similar properties occurred in keratinocytes cocultured with melanoma cells. Analysis of the individual steps indicated that activation of the metalloproteinase ADAM10 by signal peptide peptidase-like 3 (SPPL3) triggered by mutant BRAF^V600E was a critical transformation event. SPPL3-mediated ADAM10 activation involved the translocation of SPPL3 and ADAM10 into Rab4- or Rab27-positive endosomal compartments. This endosomal translocation, and hence ADAM10 activation, was inhibited by the presence of the tumor suppressor PTEN. Our findings suggest that systematic tissue antigen analysis could complement whole-genome approaches to provide more insight into cancer development.

Cross-talk between interferon-gamma and interleukin-18 in melanogenesis

Skin is the largest organ in our body and strategically placed to provide a metabolically active biological barrier against a range of noxious stressors. A lot of inflammatory cytokines, which are increased after ultraviolet (UV) irradiation produced by keratinocytes or other immunocytes, are closely related to pigmentary changes, including interleukin-18 (IL-18) and interferon-γ (IFN-γ). In this study, the effect of cross-talk between IL-18 and IFN-γ on melanogenesis was investigated. Treatment with IL-18 resulted in a dose-dependent increase of melanogenesis, while IFN-γ made an opposite effect. This influence of IL-18 and IFN-γ was mediated by regulations of microphthalmia-associated transcription factor (MITF) and its downstream enzymatic cascade expressions. Furthermore, IFN-γ inhibited basal and IL-18-induced melanogenesis. IFN-γ increased signal transducer and activator of transcription-1 (STAT-1) phosphorylation to play its position in regulating melanin pigmentation, and its inhibitory effect could be prevented by Janus Kinase 1 (JAK 1) inhibitor. IFN-γ could inhibit melanogenesis by decreasing melanocyte dendrite formation. In addition, IFN-γ inhibited the expressions of Rab Pases to suppress the mature and transport of melanosomes. IL-18 could rapidly induce Akt and PTEN phosphorylation and p65 expression in B16F10 cells. When treatment with IL-18 and IFN-γ together, the phosphorylation level of Protein Kinase B (Akt) and phosphatase and tensin homolog deleted on chromosome ten (PTEN) and expression of p65 NF-κB were inhibited, compared with treated with IL-18 only. Our studies indicated that IFN-γ could directly induce B16F10 cells apoptosis in vitro. Furthermore, we demonstrated that IFN-γ markedly up-regulated IL-18 binding protein (BP) production in normal human foreskin-derived epidermal keratinocytes in dose-dependent manner. UVB irradiation induced protease-activated receptor-2 (PAR-2) expression in NHEK, IFN-γ could inhibit this enhancement in a dose-dependent manner. These data suggest that IFN-γ plays a role in regulating inflammation- or UV-induced pigmentary changes, in direct/indirect manner.

Madecassoside inhibits melanin synthesis by blocking ultraviolet-induced inflammation

Madecassoside (MA), a pentacyclic triterpene isolated from Centella asitica (L.), is used as a therapeutic agent in wound healing and also as an anti-inflammatory and anti-aging agent. However, the involvement of MA in skin-pigmentation has not been reported. This study was conducted to investigate the effects of MA on ultraviolet (UV)-induced melanogenesis and mechanisms in a co-culture system of keratinocytes and melanocytes. MA significantly inhibited UVR-induced melanin synthesis and melanosome transfer in the co-culture system. These effects were further demonstrated by the MA-induced inhibition of protease-activated receptor-2 expression and its signaling pathway, cyclooxygenase-2, prostaglandin E2 and prostaglandin F2 alpha in keratinocytes. The clinical efficacy of MA was confirmed on artificially tanned human skin. MA significantly reduced UV-induced melanin index at 8 weeks after topical application. Overall, the study demonstrated significant benefits of MA use in the inhibition of hyperpigmentation caused by UV irradiation.

Oxidative stress status in patients with melasma

BACKGROUND

Melasma is an acquired skin disease characterized clinically by development of gray-brown macules or patches. The lesions have geographic borders and most often seen on face and less frequently on the neck and forearms. Pathogenesis has not been completely understood yet. Although the disease constitutes a very disturbing cosmetic problem, it has not obtained an efficient treatment. There were not any studies in the literature that evaluates the role of oxidative stress in melasma.

OBJECTIVES

The evaluation of the role of oxidative stress in melasma.

METHODS

Fifty melasma patients and 50 healthy volunteers were included in the study. The diagnosis was made clinically and the patients were evaluated by Melasma Area Severity Index. Superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) enzyme activities and malondialdehyde, nitric oxide, protein carbonyl levels were measured both in the melasma group and the control group.

RESULTS

SOD and GSH-Px enzyme activities were significantly higher in the patient group in comparison with the control group (p < 0.001). Protein carbonyl levels were significantly lower in the patient group (p < 0.001).

CONCLUSION

The results show that the balance between oxidant and anti-oxidants was disrupted and the oxidative stress increased in melasma. These results improve the understanding of etiology-pathogenesis of the disease and its treatment.

Pheomelanin in the skin of Hymenochirus boettgeri (Amphibia: Anura: Pipidae)

Pheomelanin is supposed to be the first type of melanin found in vertebrates, in contrast to the main type - eumelanin. Our study aimed at detecting pheomelanin in the skin of Hymenochirus boettgerii. We employed electron paramagnetic resonance (EPR) spectroscopy, and transmission electron microscopy (TEM), supplemented with standard histology and immunochemistry. We identified pheomelanin in the dorsal skin of adult frogs (not only in the dermis, but also in the epidermis) and in the dorsal tadpole. Our work identifies Hymenochirus boettgerii as a model in the basic study on the mechanism, evolution and role of melanogenesis in animals, including human.

N-Nicotinoyl dopamine, a novel niacinamide derivative, retains high antioxidant activity and inhibits skin pigmentation

We synthesized a novel derivative of a well-known skin-lightening compound niacinamide, N-nicotinoyl dopamine (NND). NND did not show inhibitory effects of tyrosinase and melanin synthesis in B16F10 mouse melanoma cells. However, NND retains high antioxidant activity without affecting viability of cells. In a reconstructed skin model, topical applications of 0.05% and 0.1% NND induced skin lightening and decreased melanin production without affecting the viability and morphology of melanocytes and overall tissue histology. Moreover, no evidence for skin irritation or sensitization was observed when 0.1% NND emulsion was applied onto the skin of 52 volunteers. The effect of NND on skin lightening was further revealed by pigmented spot analyses of human clinical trial. Overall, NND treatment may be a useful trial for skin lightening and treating pigmentary disorders.