A Zn(II)–glycine complex suppresses UVB-induced melanin production by stimulating metallothionein expression

The Enhanced Skin Permeation of Flavonoids Via the Application of a Coamorphous in a Microemulsion Formulation

Improving the permeability and solubility of poorly water-soluble compounds is a major difficulty in skin permeation. In this study, we investigated whether using a pharmaceutical technique such as applying coamorphous to a microemulsion enhances the skin permeation of polyphenolic compounds. The melt-quenching technique created the coamorphous system between naringenin (NRG) and hesperetin (HPT), two polyphenolic compounds with poor water solubility. By creating a supersaturated state, the aqueous solution of coamorphous NRG/HPT demonstrated improved NRG and HPT skin permeation. However, as both compounds precipitated, the supersaturation ratio decreased. In contrast to crystal compounds, incorporating coamorphous material into microemulsions enabled the preparation of microemulsions in a wider formulation range. Additionally, compared to microemulsions with crystal compounds and an aqueous suspension of coamorphous, microemulsions with coamorphous NRG/HPT increased skin permeation of both compounds by more than four times. These results suggested that interactions between NRG and HPT are maintained in the microemulsion and enhance both compounds' skin permeation. An approach for improving the skin permeation of poorly water-soluble chemicals would be to apply a coamorphous system to a microemulsion.

Analysis of the antimelanogenic activity of zinc and selenium in vitro

Melasma is an acquired chronic condition characterized by hyperchromic patches in photo-exposed areas. The search for new compounds for the treatment of melasma without side effects is constant. In this context, the aim of this study was to investigate the in vitro cytotoxic and antimelanogenic effects of the trace elements Zinc (Zn) and Selenium (Se). In this study, we evaluated the effects of 30 µM hydroquinone, this concentration did not alter mitochondrial function (MTT assay), but increased the percentage of necrotic cells and levels of reactive species. Furthermore, it showed no influence on tyrosinase activity and melanin content. Unlike hydroquinone, exposure for 48 h to 100 µM Zn and 1 and 5 µM Se had no significant influence on the analysis of reactive species, as well as on the percentage of necrotic cells. Still, specifically in relation to 100 µM Zn, it decreased the melanin content. Given the above, the trace elements Zn and Se did not show toxicity at the concentrations tested and Zn showed a promising effect, however, the mechanism needs to be better explored in order to contribute to new and updated research in the fight against melasma with a perspective of therapeutic use.

Daphnetin inhibits α-MSH-induced melanogenesis via PKA and ERK signaling pathways in B16F10 melanoma cells

Daphnetin is a dehydroxylated derivative of coumarin isolated from Daphne species. However, the effect of daphnetin on melanogenesis has not been elucidated. This study aims to investigate the inhibitory effect of daphnetin on melanogenesis in α-melanocyte stimulating hormone (α-MSH)-treated B16F10 cells and its potential mechanism. Melanin content analysis and cellular tyrosinase activity assay showed that daphnetin inhibited melanin biosynthesis in α-MSH-treated B16F10 cells. Immunoblotting and qRT-PCR also indicated that daphnetin suppressed the expression of microphthalmia-associated transcription factor, a mastering transcription factor of melanogenesis and its downstream melanogenic enzymes including tyrosinase and tyrosinase-related proteins. Moreover, daphnetin downregulated the phosphorylation of PKA, ERK, MSK1, and CREB. Additionally, daphnetin inhibited melanin synthesis in UVB-irradiated HaCaT conditioned medium system suggesting that daphnetin has potential as an antipigmentation activity in a physiological skin condition. Our data propose that daphnetin inhibits melanogenesis via modulating both the PKA/CREB and the ERK/MSK1/CREB pathways.

Skin biological responses to urban pollution in an ex vivo model

The skin epidermis is continuously exposed to external aggressions, including environmental pollution. The cosmetic industry must be able to offer dedicated products to fight the effects of pollutants on the skin. We set up an experimental model that exposed skin explants maintained in culture to a pollutant mixture. This mixture P representing urban pollution was designed on the basis of the French organization 'Air Parif' database. A chamber, called Pollubox®, was built to allow a controlled nebulization of P on the cultured human skin explants. We investigated ultrastructural morphology by transmission electron microscopy of high pressure frozen skin explants. A global transcriptomic analysis indicated that the pollutant mixture was able to induce relevant xenobiotic and antioxidant responses. Modulated detoxifying genes were further investigated by laser micro-dissection coupled to qPCR, and immunochemistry. Both approaches showed that P exposure correlated with overexpression of detoxifying genes and provoked skin physiological alterations down to the stratum basale. The model developed herein might be an efficient tool to study the effects of pollutants on skin as well as a powerful testing method to evaluate the efficacy of cosmetic products against pollution.

Safety assessment, biological effects, and mechanisms of Myrica rubra fruit extract for anti-melanogenesis, anti-oxidation, and free radical scavenging abilities on melanoma cells

OBJECTIVE

Currently, the cosmetic and medical industries are paying considerable attention to solve or prevent skin damage or diseases, such as hyperpigmentation and oxidation and free radical damage. In this study, the effective compounds in Myrica rubra fruit were extracted and studied the biological effects of these M. rubra fruit extracts.

METHODS

In this study, we extracted M. rubra fruit using solutions with various ratios of water to ethanol (100:0, 50:50, 5:95) and studied the anti-melanogenesis, anti-oxidation and radical scavenging effects of these M. rubra fruit extracts on two melanoma cell lines: mouse melanoma (B16-F0) and human melanoma (A2058). The cytotoxicity, melanin synthesis, mushroom and cellular tyrosinase activities, enzyme kinetics, melanogenesis-related gene expression, melanogenesis-related protein secretion, radical DPPH scavenging activity and ROS inhibition after treatment with M. rubra fruit extracts were determined.

RESULTS

The results showed that the water extract of M. rubra fruit was less cytotoxic to the melanoma cell lines, effectively inhibited melanin synthesis and tyrosinase activity and down-regulated the gene expression and protein secretion of MITF and TRP-1. In addition, the M. rubra fruit extracts also showed the abilities to scavenge DPPH free radicals and suppress ROS production. Finally, the effective compounds in the water extract were Myricetin-O-deoxyhexoside, Quercetin-O-deoxyhexoside, and Kaempferol-O-hexoside determined by LC/MS/MS assay.

CONCLUSION

Overall, the water extract of M. rubra fruit is a safe and effective melanin inhibitor and anti-oxidant and can be applied widely in the fields of cosmetics and medicine.

Cynaropicrin attenuates UVB-induced oxidative stress via the AhR-Nrf2-Nqo1 pathway

Due to its antioxidant and anti-inflammatory activities, artichoke (Cynara scolymus) has been used as folk medicine to treat various diseases. Cynaropicrin (Cyn), a sesquiterpene lactone, is the major bioactive phytochemical in the artichoke; however, its pharmacological mechanism remains unknown. Because some phytochemicals exert their antioxidant activity by activating aryl hydrocarbon receptor (AhR), leading to subsequent induction of the antioxidant pathway including nuclear factor E2-related factor 2 (Nrf2) and

NAD(P)H

quinone oxidoreductase 1 (Nqo1), we investigated whether Cyn also activates the AhR-Nrf2-Nqo1 pathway. Cyn indeed induced the activation (nuclear translocation) of AhR, leading to nuclear translocation of Nrf2 and dose-dependent upregulation of Nrf2 and Nqo1 mRNAs in human keratinocytes. The Cyn-induced AhR-Nrf2-Nqo1 activation was AhR- and Nrf2-dependent, as demonstrated by the observation that it was absent in keratinocytes transfected by siRNA against either AhR or Nrf2. In accordance with these findings, Cyn actively inhibited generation of reactive oxygen species from keratinocytes irradiated with ultraviolet B (UVB) in a Nrf2-dependent manner. Cyn also inhibited the production of proinflammatory cytokines such as interleukin 6 and tumor necrosis factor-α from UVB-treated keratinocytes. Our findings demonstrate that Cyn is a potent activator of the AhR-Nrf2-Nqo1 pathway, and could therefore be applied to prevention of UVB-induced photo aging.

Shining light on skin pigmentation: the darker and the brighter side of effects of UV radiation

The term barrier function as applied to human skin often connotes the physical properties of this organ that provides protection from its surrounding environment. This term does not generally include skin pigmentation. However, skin pigmentation, which is the result of melanin produced in melanocytes residing in the basal layer of the skin and exported to the keratinocytes in the upper layers, serves equally important protective function. Indeed, changes in skin pigmentation are often the most readily recognized indicators of exposure of skin to damaging agents, especially to natural and artificial radiation in the environment. Several recent studies have shed new light on (1) the mechanisms involved in selective effects of subcomponents of UV radiation on human skin pigmentation and (2) the interactive influences between keratinocytes and melanocytes, acting as "epidermal melanin unit," that manifest as changes in skin pigmentation in response to exposure to various forms of radiation. This article provides a concise review of our current understanding of the effects of the nonionizing solar radiation, at cellular and molecular levels, on human skin pigmentation.

The two faces of metallothionein in carcinogenesis: photoprotection against UVR-induced cancer and promotion of tumour survival

Metallothionein is a multi-functional protein that protects the host against toxic heavy metals. Under stressful situations it can protect against oxidative damage, contribute to tissue repair, modulate immune responses and limit inflammatory processes. Recently, metallothionein's role in ultraviolet radiation (UVR)-induced injury has been investigated. These studies have shown that when metallothionein is upregulated following exposure to UVR, it can protect against UVR-induced damage and the subsequent development of skin cancer. We propose that this initial protection is achieved through its anti-oxidant role resulting in reduced oxidative stress, reduced apoptosis, reduced NFkappaB activation and enhanced repair of DNA damage. However, once UVR-induced neoplasia has occurred, the cancer cells can hijack metallothionein's protective functions, resulting in increased tumour progression and malignancy. These two discordant sets of attributes are context-dependent, and represent the two faces of metallothionein.

Role of antioxidants in the skin: anti-aging effects

Intracellular and extracellular oxidative stress initiated by reactive oxygen species (ROS) advance skin aging, which is characterized by wrinkles and atypical pigmentation. Because UV enhances ROS generation in cells, skin aging is usually discussed in relation to UV exposure. The use of antioxidants is an effective approach to prevent symptoms related to photo-induced aging of the skin. In this review, the mechanisms of ROS generation and ROS elimination in the body are summarized. The effects of ROS generated in the skin and the roles of ROS in altering the skin are also discussed. In addition, the effects of representative antioxidants on the skin are summarized with a focus on skin aging.