Melanin is a biopolymer implicated in the protection of cellular membranes and DNA produced by melanocytes. This pigment has a dual role and should be considered as a photo-protector and as a photosensitizer due to it...Melanin is a biopolymer implicated in the protection of cellular membranes and DNA produced by melanocytes. This pigment has a dual role and should be considered as a photo-protector and as a photosensitizer due to its interaction with UV. The design of multifunctional and biologically responsive coatings is of major interest in modern biomaterials science. The aim of this study is not only to characterize the deposition of multilayered polyelectrolytes films made from polydopamine particles and polyamines like poly-(L-lysine hydrobromide) (PLL), but also to evaluate melanoma cells activity in terms of proliferation and their capacity to stimulate melanin secretion. One could expect that the presence of a melanin like material in the film may have a positive or a negative feedback on the melanin biosynthesis and consequently on melanoma development. Some comparisons are also done with pure polydopamine grains in suspension in the cell culture medium, to investigate if the immobilization of the polydopamine grains has an influence on their bioactivity.展开更多
Melanin, synthesized by melanocyte, is transferred to neighboring keratinocyte and finally accumulates in perinuclear site. Except functioning as an internal sunscreen to protect from UV damage, the potential effect o...Melanin, synthesized by melanocyte, is transferred to neighboring keratinocyte and finally accumulates in perinuclear site. Except functioning as an internal sunscreen to protect from UV damage, the potential effect of melanin on modulating the bioactivity of keratinocyte has not yet been fully investigated. In this study, we added melanin directly to the culture of human epidermal keratinocytes and the uptake of melanin was found to be dose- and time-dependent as determined by spectrophotometric method. The uptaken melanin accumulated perinuclearly in keratinocytes that is similar to the pattern observed in human solar lentigo tissue by microscopic examination. Pretreatment of keratinocytes with either niacinamide or trypsin inhibitor reduced the uptake of melanin dose-dependently, indicating a PAR-2-dependent pathway involved. Melanin uptake by keratinocytes inhibited cell proliferation as demonstrated both by the decrease of cell number and nuclear Ki-67 expression. Inhibited Ki-67 expression in melanin-containing keratinocyte was also found in human lentigo tissue. The cell cycle arrested at G1 phase in melanin-uptaken keratinocytes was confirmed by flow cytometric method. The protein expressions of cyclin-dependent kinase 1 (CDK1), CDK2, cyclin E, cyclin A and cyclin B were significantly reduced by melanin treatment. Microarray analysis, RT/real-time PCR and western blot demonstrated the inhibited expression of DKK1, a protein known to reduce skin pigmentation, in melanin-uptaken keratinocytes. Together, the direct incubation of keratinocyte with melanin might serve as a useful model to study the potential mechanisms involved in melanin uptake and pigmentation process.展开更多
Melanocytes that form stratum basale of skin epidermis express tyrosinase enzyme, which catalyzes initial two rate-limiting steps in the biotransformation of tyrosine into dark pigment called melanin. Even today, Tyro...Melanocytes that form stratum basale of skin epidermis express tyrosinase enzyme, which catalyzes initial two rate-limiting steps in the biotransformation of tyrosine into dark pigment called melanin. Even today, Tyrosinase inhibitors are among the promising candidates in cosmetic industry for skin-lightening formulations. Overexpression of tyrosinase causes excess melanin biosynthesis and deposition resulting in dark skin color. Moreover, localized overexpression of tyrosinase cause variety of hyperpigmentation disorders like melanoma, melasma, chloasma, dark patches, liver patches, etc. There has been a renewed interest in the natural products as main ingredients in the formulation of safe products for skin-whitening and treatment options for hyperpigmentation disorders. In the present communication, the results of our investigations on tyrosinase inhibition, modulation of intracellular tyrosinase and melanin levels in cultured B16F10 melanoma cells by Bacopa monnieri (L.) methanol extract (BME) are presented and discussed as safe option for skin lightening and to treat hyperpigmentation disorders. BME showed 11%, 29%, 54% and 80% inhibition of mushroom tyrosinase activity at an initial 100, 200, 400 and 600 μg of extract. Treatment of α-melanocyte stimulating hormone (α-MSH) stimulated cultured murine melanoma B16F10 cells with 100 μg/ml of the extract showed a decrease in the levels of cellular melanin and cellular tyrosinase content by 22% and 46% respectively. The cytotoxicity studies by MTT assay revealed that the LC50 of the BME is ≥1000 μg/ml in cultured mouse melanoma B16F10 and HEK293 cells.展开更多
文摘Melanin is a biopolymer implicated in the protection of cellular membranes and DNA produced by melanocytes. This pigment has a dual role and should be considered as a photo-protector and as a photosensitizer due to its interaction with UV. The design of multifunctional and biologically responsive coatings is of major interest in modern biomaterials science. The aim of this study is not only to characterize the deposition of multilayered polyelectrolytes films made from polydopamine particles and polyamines like poly-(L-lysine hydrobromide) (PLL), but also to evaluate melanoma cells activity in terms of proliferation and their capacity to stimulate melanin secretion. One could expect that the presence of a melanin like material in the film may have a positive or a negative feedback on the melanin biosynthesis and consequently on melanoma development. Some comparisons are also done with pure polydopamine grains in suspension in the cell culture medium, to investigate if the immobilization of the polydopamine grains has an influence on their bioactivity.
文摘Melanin, synthesized by melanocyte, is transferred to neighboring keratinocyte and finally accumulates in perinuclear site. Except functioning as an internal sunscreen to protect from UV damage, the potential effect of melanin on modulating the bioactivity of keratinocyte has not yet been fully investigated. In this study, we added melanin directly to the culture of human epidermal keratinocytes and the uptake of melanin was found to be dose- and time-dependent as determined by spectrophotometric method. The uptaken melanin accumulated perinuclearly in keratinocytes that is similar to the pattern observed in human solar lentigo tissue by microscopic examination. Pretreatment of keratinocytes with either niacinamide or trypsin inhibitor reduced the uptake of melanin dose-dependently, indicating a PAR-2-dependent pathway involved. Melanin uptake by keratinocytes inhibited cell proliferation as demonstrated both by the decrease of cell number and nuclear Ki-67 expression. Inhibited Ki-67 expression in melanin-containing keratinocyte was also found in human lentigo tissue. The cell cycle arrested at G1 phase in melanin-uptaken keratinocytes was confirmed by flow cytometric method. The protein expressions of cyclin-dependent kinase 1 (CDK1), CDK2, cyclin E, cyclin A and cyclin B were significantly reduced by melanin treatment. Microarray analysis, RT/real-time PCR and western blot demonstrated the inhibited expression of DKK1, a protein known to reduce skin pigmentation, in melanin-uptaken keratinocytes. Together, the direct incubation of keratinocyte with melanin might serve as a useful model to study the potential mechanisms involved in melanin uptake and pigmentation process.
文摘Melanocytes that form stratum basale of skin epidermis express tyrosinase enzyme, which catalyzes initial two rate-limiting steps in the biotransformation of tyrosine into dark pigment called melanin. Even today, Tyrosinase inhibitors are among the promising candidates in cosmetic industry for skin-lightening formulations. Overexpression of tyrosinase causes excess melanin biosynthesis and deposition resulting in dark skin color. Moreover, localized overexpression of tyrosinase cause variety of hyperpigmentation disorders like melanoma, melasma, chloasma, dark patches, liver patches, etc. There has been a renewed interest in the natural products as main ingredients in the formulation of safe products for skin-whitening and treatment options for hyperpigmentation disorders. In the present communication, the results of our investigations on tyrosinase inhibition, modulation of intracellular tyrosinase and melanin levels in cultured B16F10 melanoma cells by Bacopa monnieri (L.) methanol extract (BME) are presented and discussed as safe option for skin lightening and to treat hyperpigmentation disorders. BME showed 11%, 29%, 54% and 80% inhibition of mushroom tyrosinase activity at an initial 100, 200, 400 and 600 μg of extract. Treatment of α-melanocyte stimulating hormone (α-MSH) stimulated cultured murine melanoma B16F10 cells with 100 μg/ml of the extract showed a decrease in the levels of cellular melanin and cellular tyrosinase content by 22% and 46% respectively. The cytotoxicity studies by MTT assay revealed that the LC50 of the BME is ≥1000 μg/ml in cultured mouse melanoma B16F10 and HEK293 cells.
