Hyperpigmentation mechanism of methyl 3,5-di-caffeoylquinate through activation of p38 and MITF induction of tyrosinase

Transcriptomic and Physiological Analysis Reveal Melanin Synthesis-Related Genes and Pathways in Pacific Oysters (Crassostrea gigas)

Shell color is one of the shell traits of molluscs, which has been regarded as an economic trait in some bivalves. Pacific oysters (Crassostrea gigas) are important aquaculture shellfish worldwide. In the past decade, several shell color strains of C. gigas were developed through selective breeding, which provides valuable materials for research on the inheritance pattern and regulation mechanisms of shell color. The inheritance patterns of different shell colors in C. gigas have been identified in certain research; however, the regulation mechanism of oyster pigmentation and shell color formation remains unclear. In this study, we performed transcriptomic and physiological analyses using black and white shell oysters to investigate the molecular mechanism of melanin synthesis in C. gigas. Several pigmentation-related pathways, such as cytochrome P450, melanogenesis, tyrosine metabolism, and the cAMP signaling pathway were found. The majority of differentially expressed genes and some signaling molecules from these pathways exhibited a higher level in the black shell oysters than in the white, especially after L-tyrosine feeding, suggesting that those differences may cause a variation of tyrosine metabolism and melanin synthesis. In addition, the in vitro assay using primary cells from mantle tissue showed that L-tyrosine incubation increased cAMP level, gene and protein expression, and melanin content. This study reveals the difference in tyrosine metabolism and melanin synthesis in black and white shell oysters and provides evidence for the potential regulatory mechanism of shell color in oysters.

Carotenoids in red fruit (Pandanus conoideus Lam.) have a potential role as an anti‑pigmentation agent (Review)

Melasma is a persistent condition characterized by excessive melanin production in the skin. The management of melasma necessitates a protracted treatment duration, which is associated with diminished levels of patient satisfaction. One effective strategy for mitigating occurrence of melasma is consumption of nutricosmetics with depigmentation properties. The present review aimed to investigate the potential of red fruit as a depigmentation agent. Carotenoids serve a crucial role in human nutrition as a precursor to vitamin A. Carotenoids serve as scavengers of reactive oxygen species generated by ultraviolet radiation. Carotenoids promote skin health. Red fruit, a fruit originating from Papua (Indonesia) has anti-pigmentation properties associated with its ability to block melanogenesis through various protein pathways such as PKA, ERK, and AKT signaling pathways. The consumption of food rich in carotenoids, such as red fruit, has advantageous properties to reduce hyperpigmentation and skin brightening.

Microarray meta-analysis reveals comprehensive effects of 3,4,5-tricaffeolyquinic acid in cell differentiation and signaling

Caffeoylquinic acids (CQA) are polyphenolic compounds found in fruits, vegetables, coffee, and spices that have exhibited several beneficial activities, including antioxidant, antibacterial, neuroprotective, anti-inflammatory, anticancer, antiviral, antidiabetic, and cardiovascular effects. A derivative, TCQA (3,4,5-Tri-O-caffeoylquinic acid), has also shown both neurogenic and pigment differentiation potential. A transcriptomic-based meta-analysis was conducted to explore potential biochemical processes and molecular targets of TCQA. This approach involved integrating data from various cell and tissue types, including human amniotic stem cells, human neural stem cells, human dermal papilla cells, and the brain cortex of aging model mice. It offered a comprehensive perspective on the significant gene regulations in response to TCQA treatment. The objective was to uncover the mechanism and novel targets of TCQA, facilitating a further understanding of its functions. New areas of interest found were TCQA's effect on adipogenesis, heart, and muscle tissue development. In addition, significantly enhanced biological activities found through meta-analysis included cell cycle, VEGFA-VEGFR2 pathway, and BMP signaling. Overall, a comprehensive functional and visual analysis using available biological databases uncovered the multi-target potential of this natural compound.

Research Progress of Small Molecules as Anti-vitiligo Agents

Vitiligo is a disease characterized by skin discoloration, and no safe and effective drugs have been developed until now. New drug research and development are imminent. This article reviews the research on small-molecule drugs for vitiligo from 1990 to 2021 at home and abroad. They are classified according to their structures and mechanisms of action, including natural products and derivatives, anti-oxidative stress drugs, immunosuppressants, prostaglandins, etc. The research on their anti-vitiligo activity, structural modification, new dosage forms, clinical trials, and the development trend in new anti-vitiligo drugs are reviewed, which provides important references for the development of new drugs.

The Modulation of Melanogenesis in B16 Cells Upon Treatment with Plant Extracts and Isolated Plant Compounds

Plants are a rich source of secondary metabolites that exhibit numerous desired properties. The compounds may influence the biology of melanocytes, pigment cells that produce melanin, by modulating numerous signaling pathways, including cAMP/PKA, MAPKs and PI3K/AKT. Its downstream target is microphthalmia-associated transcription factor, responsible for the expression of the tyrosinase enzyme, which plays a major role in melanogenesis. Therefore, this literature review aims to provide insights related to melanogenesis modulation mechanisms of plant extracts and isolated plant compounds in B16 cells. Database searches were conducted using online-based library search instruments from 2012 to 2022, such as NCBI-PubMed and Google Scholar. Upregulation or downregulation of signaling pathways by phytochemicals can influence skin hypo- and hyperpigmentation by changing the level of melanin production, which may pose a significant cosmetic issue. Therefore, plant extracts or isolated plant compounds may be used in the therapy of pigmentation disorders.

Dimethyl Itaconate Reduces α-MSH-Induced Pigmentation via Modulation of AKT and p38 MAPK Signaling Pathways in B16F10 Mouse Melanoma Cells

Dimethyl itaconate (DMI) exhibits an anti-inflammatory effect. Activation of nuclear factor erythroid 2-related factor 2 (NRF2) is implicated in the inhibition of melanogenesis. Therefore, DMI and itaconic acid (ITA), classified as NRF2 activators, have potential uses in hyperpigmentation reduction. The activity of cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB), an important transcription factor for MITF gene promoter, is regulated by glycogen synthase kinase 3β (GSK3β) and protein kinase A (PKA). Here, we investigated the inhibitory effect of ITA and DMI on alpha-melanocyte-stimulating hormone (α-MSH)-induced MITF expression and the modulatory role of protein kinase B (AKT) and GSK3β in melanogenesis in B16F10 mouse melanoma cells. These cells were incubated with α-MSH alone or in combination with ITA or DMI. Proteins were visualized and quantified using immunoblotting and densitometry. Compared to ITA, DMI treatment exhibited a better inhibitory effect on the α-MSH-induced expression of melanogenic proteins such as MITF. Our data indicate that DMI exerts its anti-melanogenic effect via modulation of the p38 mitogen-activated protein kinase (MAPK) and AKT signaling pathways. In conclusion, DMI may be an effective therapeutic agent for both inflammation and hyperpigmentation.

Research Progress on Targeted Antioxidant Therapy and Vitiligo

Vitiligo is a common acquired depigmenting disease characterized by the loss of functional melanocytes and epidermal melanin. Vitiligo has a long treatment cycle and slow results, which is one of the most difficult challenges for skin diseases. Oxidative stress plays an important role as an initiating and driving factor in the pathogenesis of vitiligo. Antioxidant therapy has recently become a research hotspot in vitiligo treatment. A series of antioxidants has been discovered and applied to the treatment of vitiligo, which has returned satisfactory results. This article briefly reviews the relationship between oxidative stress and vitiligo. We also describe the progress of targeted antioxidant therapy in vitiligo, with the aim of providing a reference for new drug development and treatment options for this condition.

Plant-Derived Compounds as Promising Therapeutics for Vitiligo

Vitiligo is the most common depigmenting disorder characterized by white patches in the skin. The pathogenetic origin of vitiligo revolves around autoimmune destruction of melanocytes in which, for instance, oxidative stress is responsible for melanocyte molecular, organelle dysfunction and melanocyte specific antigen exposure as well as melanocyte cell death and thus serves as an important contributor for vitiligo progression. In recent years, natural products have shown a wide range of pharmacological bioactivities against many skin diseases, and this review focuses on the effects and mechanisms of natural compounds against vitiligo models. It is showed that some natural compounds such as flavonoids, phenols, glycosides and coumarins have a protective role in melanocytes and thereby arrest the depigmentation, and, additionally, Nrf2/HO-1, MAPK, JAK/STAT, cAMP/PKA, and Wnt/β-catenin signaling pathways were reported to be implicated in these protective effects. This review discusses the great potential of plant derived natural products as anti-vitiligo agents, as well as the future directions to explore.

Regulating cell fate of human amnion epithelial cells using natural compounds: an example of enhanced neural and pigment differentiation by 3,4,5-tri-O-caffeoylquinic acid

Over the past years, Human Amnion Epithelial Cells (hAECs), a placental stem cell, are gaining higher attention from the scientific community as they showed several advantages over other types of stem cells, including availability, easy accessibility, reduced rejection rate, non-tumorigenicity, and minimal legal constraint. Recently, natural compounds are used to stimulate stem cell differentiation and proliferation and to enhance their disease-treating potential. A polyphenolic compound 3,4,5-Tri-O-Caffeoylquinic Acid (TCQA) has been previously reported to induce human neural stem cell differentiation and may affect melanocyte stem cell differentiation as well. In this study, TCQA was tested on 3D cultured hAECs after seven days of treatment, and then, microarray gene expression profiling was conducted of TCQA-treated and untreated control cells on day 0 and day 7. Analyses revealed that TCQA treatment significantly enriched pigment and neural cells sets; besides, genes linked with neurogenesis, oxidation-reduction process, epidermal development, and metabolism were positively regulated. Interestingly, TCQA stimulated cell cycle arrest-related pathways and differentiation signaling. On the other hand, TCQA decreased interleukins and cytokines expression and this due to its anti-inflammatory properties as a polyphenolic compound. Results were validated to highlight the main activities of TCQA on hAECs, including differentiation, cell cycle arrest, and anti-inflammatory. This study highlights the important role of hAECs in regenerative medicine and the use of natural compounds to regulate their fate. Video abstract.

Asoprisnil, a Selective Progesterone Receptor Modulator (SPRM), Inhibits Melanosome Export in B16F10 Cells and HEMn-DP Melanocytes

Previous studies have reported that estrogen hormone promotes melanogenesis while progesterone inhibits it. A selective estrogen receptor modulator (SERM), tamoxifen, has been shown to promote melanogenesis; however, to date, there have been no reports on the effects of a selective progesterone receptor modulator (SPRM) on melanogenesis. In the present study, we hypothesized that asoprisnil (AP), a SPRM, inhibits melanogenesis. AP was tested for cytotoxicity to B16F10 mouse melanoma cells for screening the nontoxic concentrations using MTS cytotoxicity assay. Extracellular and intracellular melanin levels were estimated at nontoxic concentrations of AP. To evaluate the direct effect of AP on tyrosinase enzyme, tyrosinase activity and copper chelating activities were measured. Next, the effects of AP on melanogenesis were tested in normal human melanocytes, neonatal, darkly pigmented (HEMn-DP). Our results demonstrate that AP was nontoxic at a concentration range of 10–50 μM in B16F10 cells; AP at 50 μM significantly suppressed extracellular melanin levels comparable to kojic acid at 500 μM, with no significant effect on intracellular melanin levels. The mechanism of melanogenesis inhibition was studied to assess if AP downregulated tyrosinase activity in cell lysates or in a cell-free system. However, AP was found to increase intracellular tyrosinase activity without any effect on tyrosinase enzyme activity or copper chelating activity in a cell-free system, indicating that AP inhibits melanogenesis by mechanisms other than direct effects on tyrosinase enzyme activity. The capacity of AP to inhibit melanosome export was further validated in HEMn-DP cells; AP significantly suppressed dendricity at concentrations of 20 and 30 μM in the absence of effects on melanin synthesis or intracellular tyrosinase activity. In addition, AP was nontoxic to human keratinocytes (HaCaT) at these concentrations, validating its safety for topical use. Taken together, our preliminary results demonstrate that AP might be repurposed as a candidate therapeutic for treatment of hyperpigmentation disorders via a unique mechanism, which encompasses a selective inhibition of melanosome export.

β-catenin-mediated hair growth induction effect of 3,4,5-tri-O-caffeoylquinic acid

The hair follicle is a complex structure that goes through a cyclic period of growth (anagen), regression (catagen), and rest (telogen) under the regulation of several signaling pathways, including Wnt/ β-catenin, FGF, Shh, and Notch. The Wnt/β-catenin signaling is specifically involved in hair follicle morphogenesis, regeneration, and growth. β-catenin is expressed in the dermal papilla and promotes anagen induction and duration, as well as keratinocyte regulation and differentiation. In this study, we demonstrated the activation of β-catenin by a polyphenolic compound 3,4,5-tri-O-caffeoylquinic acid (TCQA) in mice model and in human dermal papilla cells to promote hair growth cycle. A complete regrowth of the shaved area of C3H mice was observed upon treatment with TCQA. Global gene expression analysis using microarray showed an upregulation in hair growth-associated genes. Moreover, the expression of β-catenin was remarkably upregulated in vivo and in vitro. These findings suggest that β-catenin activation by TCQA promoted the initiation of the anagen phase of the hair cycle.

3,4,5-Tri-O-Caffeoylquinic Acid Promoted Hair Pigmentation Through β-Catenin and Its Target Genes

The hair follicle undergoes a regular cycle composed of three phases: anagen, catagen, and telogen. The life of follicular melanocytes is totally linked to the hair cycle; and during anagen or the growth phase, the melanocytes are active and produce the melanin responsible of hair shaft pigmentation. Various signaling pathways regulate the hair growth cycle and, therefore, the pigmentation; we distinguish the Wnt/β-catenin signaling pathway as it plays a major role in the development, growth, and proliferation of the melanocytes and the activation of melanogenesis enzymes and the related transcription factor. In this study, 3,4,5-tri-O-caffeoylquinic acid (TCQA), a caffeoylquinic acid derivative, stimulated the pigmentation in C3H mouse hair follicle, in human melanocytes, and B16F10 melanoma cells. An enhancement in pigmentation associated genes was observed upon TCQA treatment in vivo and in vitro. Interestingly, the expression of β-catenin was remarkably upregulated in mouse treated skin and in pigment cell lines. Moreover, TCQA upregulated CTNNB1 expression after inhibition in human melanocytes. Taken together, this study suggests that TCQA triggered β-catenin activation to enhance the pigmentation during the anagen phase of the hair cycle.

p38 MAPK is involved in the immune response to pathogenic Vibrio in the clam Meretrix petechialis

p38 mitogen-activated protein kinases (MAPKs) are involved in the response to various extracellular stimuli via regulating gene expression. In the present study, a p38 MAPK gene (MpP38) was identified from the clam Meretrix petechialis. The full-length cDNA of MpP38 measures 1,720 bp, consisting of a 134-bp 5'-UTR, a 1,095-bp ORF and a 491-bp 3'-UTR. Both the mRNA and protein expression levels of MpP38 increased after Vibrio challenge, implying that MpP38 is involved in clam immunity. Based on our previous study, a transcription factor activated by p38 MAPK, i.e. microphthalmia-associated transcription factor (MITF), participated in clam immunity by regulating the expression of phenoloxidase (PO). Coupled with other related reports, the mechanism underlying the involvement of MpP38 in clam immunity is most likely that pathogen stimuli induce the phosphorylation of p38 MAPK and thus activate MITF to regulate the expression of the immune-related gene PO. The results obtained in this study support this mechanism. First, we found that the MpP38 phosphorylation level increased in response to Vibrio challenge. Second, as revealed by a yeast two-hybrid assay, there was a direct interaction between MpP38 and MITF. Meanwhile, inhibiting the phosphorylation of MpP38 decreased the phosphorylation level of MpMITF, implying that MpP38 phosphorylation is required for MpMITF activation. Additionally, our results showed that there was a regulatory relationship between MpP38 phosphorylation level and PO expression level. With increased MpP38 phosphorylation level, the PO expression level was also increased after Vibrio challenge; when MpP38 phosphorylation was inhibited, the PO expression level was significantly decreased. This study describes the immune function of p38 MAPK in the clam for the first time and analyses its potential underlying mechanism, which will help to elucidate the immune mechanism in the clam M. petechialis.

Nilotinib induction of melanogenesis via reactive oxygen species-dependent JNK activation in B16F0 mouse melanoma cells

Nilotinib (AMN), a second-generation tyrosine kinase inhibitor, induces apoptosis in various cancer cells, and our recent study showed that AMN effectively reduced the viability of human ovarian cancer cells via mitochondrion-dependent apoptosis. The effect of AMN in the melanogenesis of melanoma cells is still unclear. In the present study, we found that the addition of AMN but not imatinib (STI) significantly increased the darkness of B16F0 melanoma cells, and the absorptive value increased with the concentration of AMN. A decrease in the viability of B16F0 cells by AMN was detected in a concentration-dependent manner, accompanied by increased DNA ladders, hypodiploid cells and cleavage of the caspase-3 protein. An in vitro tyrosinase (TYR) activity assay showed that increased TYR activity by AMN was detected in a concentration-dependent manner; however, induction of TYR activity by STI at a concentration of 40 μmol/L was observed. Increased intracellular peroxide by AMN was detected in B16F0 cells, and application of the antioxidant, N-acetylcysteine (NAC), significantly reduced AMN-induced peroxide production which also reduced the darkness of B16F0 cells. Additionally, AMN induced c-Jun N-terminal kinase (JNK) protein phosphorylation in B16F0 cells, which was inhibited by the addition of NAC. AMN-induced melanogenesis of B16F0 cells was significantly inhibited by the addition of NAC and the JNK inhibitor, SP600125 (SP). Data of Western blotting showed that increased protein levels of melanogenesis-related enzymes of tyrosinase-related protein-1 (TRP1), TRP2 and TYR were observed in AMN-treated B16F0 cells which were inhibited by the addition of NAC and SP. Evidence is provided supporting AMN effectively inducing the melanogenesis of B16F0 melanoma cells via reactive oxygen species-dependent JNK activation.

Amine derivatives of furocoumarin induce melanogenesis by activating Akt/GSK-3β/β-catenin signal pathway

Background

Melanogenesis, or the biosynthesis of melanin, plays a critical role in the pigmentation of skin, hair, and eyes. Reduced melanogenesis may lead to depigmentation conditions such as vitiligo. Psoralen, a furocoumarin derivative, is closely associated with melanogenesis, and its derivative 8-methoxypsoralen is used in psoralen and ultraviolet A therapy for pigmentation disorders. In a previous study, we synthesized a new series of amine derivatives of furocoumarin, of which 5-(morpholinomethyl)-3-phenyl-7H-furo[3,2-g]chromen-7-one (encoded as D206008) showed a remarkable melanogenic effect in B16 murine cells.

Methods

In this study, we examined the effects of D206008 on the melanogenesis-related pathways in B16 cells. D206008 increased melanin production and tyrosinase (TYR) activity, as well as the mRNA and protein expression levels of the melanogenic enzymes TYR, TRP-1 and TRP-2, and the melanogenesis-related transcription factor microphthalmia-associated transcription factor (MITF) in a dose-dependent (0–100 µM) and time-dependent (0–48 hours) manner.

Results

Mechanistically, D206008 inhibited β-catenin degradation by enhancing the phosphorylation of Akt and glycogen synthase kinase-3β (GSK-3β), which increased the accumulation of β-catenin in the cytoplasm. Nuclear translocation of β-catenin also increased in response to D206008 treatment.

Conclusion

Taken together, these data indicate that D206008 promotes melanin synthesis by stimulating the nuclear translocation of β-catenin, which activates MITF transcription and eventually melanogenesis.

Preparation of novel 1,2,3-triazole furocoumarin derivatives via click chemistry and their anti-vitiligo activity

The extracts of Psoralea corylifolia L. were often used for the repigmentation of leukoderma (vitiligo) in traditional Uygur medicine thousands years ago. Nowadays, its active ingredient, furocoumarins, has been clinically applied since it exhibited strong photosensitivity. Thus, a new series of furocoumarin derivatives (8a-8o) containing 1,2,3-triazole were designed and synthesized based on our previous work. After biological evaluation for melanin contents and tyrosinase activity in B16 murine cells, the SAR was summarized. The results indicated that five compounds (8a, 8j, 8m-8o) were more potent than the positive control (8-MOP) on melanogenesis. Among them, 8a and 8o showed the best stimulating effect on tyrosinase activity as well, and were submitted for further pharmacological study of anti-vitiligo.

Potential anti-vitiligo properties of cynarine extracted from Vernonia anthelmintica (L.) Willd

Vitiligo is a depigmentation disorder of the skin. It is primarily caused by the destruction of melanocytes or obstruction of the melanin synthesis pathway. Melanin is a type of skin pigment that determines skin color. The seeds of Vernonia anthelmintica (L.) Willd (Kaliziri) are used for treating skin diseases including vitiligo in traditional Uyghur medicine. 1,5‑Dicaffeoylquinic acid (1,5‑diCQA) is a natural polyphenolic compound widely distributed in plants and extracted from Kaliziri seeds. Therefore, in the present study, the effect of 1,5‑diCQA on melanin synthesis in B16 cell was evaluated, and its molecular mechanism was explored. The results indicated that 1,5‑diCQA treatment of B16 cells stimulated an increase of intracellular melanin level and tyrosinase (TYR) activity without cytotoxicity. Reverse transcription quantitative polymerase chain reaction results also indicated that 1,5‑diCQA may markedly improve the protein expression and RNA transcription of microphthalmia‑associated transcription factor (MITF), melanogenic enzyme Tyr, tyrosinase‑related protein 1 (TRP 1) and tyrosinase‑related protein 2 (TRP 2). Additional results identified that 1,5‑diCQA may promote the phosphorylation of p38 mitogen‑activated protein kinase (p38 MAPK) and extracellular signal‑regulated kinase (ERK) MAPK. Notably, the increased levels of intracellular melanin synthesis and tyrosinase expression induced by 1,5‑diCQA treatment were significantly attenuated by the protein kinase A (PKA) inhibitor H‑89. Intracellular cyclic adenosine monophosphate (cAMP) concentration and phosphorylation of cAMP‑response element binding protein was increased following 1,5‑diCQA treatment. These results indicated that 1,5‑diCQA stimulated melanogenesis via the MAPK and cAMP/PKA signaling pathways in B16 cells, which has potential therapeutic implications for vitiligo.

The Effect of Volatile Oil from Vernonia anthelmintica Seeds on Melanin Synthesis in B16 Cells and Its Chemical Analysis by GC-QTOF-MS

Vernonia anthelmintica Willd. seeds have been used in folk medicine for the treatment of leukoderma in Xinjiang, China, for more than 300 years. The promoting activities of its volatile oil (AVO) in melanogenesis and its chemical composition were investigated in this paper. The bioactivities of AVO were examined by melanin synthesis and tyrosinase activity assay in B16 cells. Using GC-QTOF-MS technology, each compound of AVO contains a single separated peak in GC and the retention indices of every GC peak were calculated by the retention times of C7~C30 n-alkanes that were injected at the same chromatographic conditions. Then each individual peak was identified by comparing its mass spectrum with the MS library (NIST 14). As a result, AVO increased the melanin content and tyrosinase activity in a dose-dependent manner at concentrations of 10-30μg·mL⁻¹. The 64 compounds were identified in AVO which occupied 95.15% of total peak area in GC. They mainly contained caryophyllene (23.73%), sabinene (18.15%), α-thujene (6.57%), thymol (5.29%), 4-epi-α-acoradiene (4.98%), limonene (4.92%), anethole (3.44%), etc. According to the results the AVO can promote melanogenesis and upregulate tyrosinase activity in B16 cells.

Novel Furocoumarin Derivatives Stimulate Melanogenesis in B16 Melanoma Cells by Up-Regulation of MITF and TYR Family via Akt/GSK3β/β-Catenin Signaling Pathways

The extracts of Ficuscarica L. and Psoralen corylifolia L. are traditional Uygur medicines for the treatment of vitiligo, and its active ingredients furocoumarins, were are found to be the most effective agents against this skin disorder nowadays. Therefore, a series of novel easter derivatives (8a-8p) of furocoumarin were designed and synthesized based on our previous research to improve this activity in the present study. The synthesized derivatives were biologically evaluated for melanin synthesis in murine B16 cells and the SAR (structure-activity relationship) was summarized. Eight derivatives were more potent than positive control (8-MOP, 8-methoxypsoralan), especially compounds 8n (200%) and 8o (197%), which were nearly 1.5-fold potency when compared with 8-MOP (136%). Furthermore, the signaling pathway by which 8n activates the melanin biosynthesis was defined. Our results showed that it not only elevated the melanin content, but also stimulated the activity of tyrosinasein a concentration-dependent manner. Increasing of phosphorylation of Akt (also named PKB, protein kinase B) and non-activated GSK3β (glycogen synthase kinase 3 beta), which inhibited the degradation of β-catenin were observed through Western blot analysis. The accumulation of β-catenin probably led to the activation of transcription of MITF (microphthalmia-associated transcription factor) and TYR (tyrosinase) family, as well as the subsequent induction of melanin synthesis.

A novel psoralen derivative-MPFC enhances melanogenesis via activation of p38 MAPK and PKA signaling pathways in B16 cells

As an active compound, psoralen is present in various Chinese herbal medicines and has exhibited significant activity in skin disease treatment. Its derivative 8-methoxypsoralan (8-MOP) is the most commonly used drug to induce repigmentation of vitiligo. In our previous screening assays, 4-methyl-6-phenyl-2H-furo[3,2-g]chromen-2-one (MPFC), a psoralen derivative, was identified as more effective tyrosinase and melanin activator than the positive control 8-MOP in consideration of low doses, as well as low toxicity. The overall purpose of this study was to characterize the melanogenic effect and mechanisms of MPFC in B16 cells. The melanin biosynthesis effects of MPFC were determined by examination of cellular melanin contents, tyrosinase activity assay, cyclic adenosinemonophosphate (cAMP) assay, and western blotting of MPFC-stimulated B16 mouse melanoma cells. Our results showed that MPFC enhanced both melanin synthesis and tyrosinase activity in a concentration-dependent manner as well as significantly activated the expression of melanogenic proteins such as tyrosinase, tyrosinase-related protein-1 and tyrosinase-related protein-2. Western blot analysis showed that MPFC increased the phosphorylation of p38 mitogen-activated protein kinase and cAMP response element-binding protein (CREB) as well as the expression of microphthalmia-associated transcription factor (MITF). Moreover, MPFC stimulated intracellular cAMP levels and induced tyrosinase activity and melanin synthesis were attenuated by H89, a protein kinase A inhibitor. These results indicated that MPFC-mediated activation of the p38 MAPK and the protein kinase A (PKA) pathway may shed light on a novel approach for an effective therapy for vitiligo.

Diversity-oriented synthesis of amide derivatives of tricyclic thieno[2,3-d]pyrimidin-4(3H)-ones and evaluation of their influence on melanin synthesis in murine B16 cells

A diversity-oriented synthesis of amide-containing thieno[2,3-d]pyrimidin-4(3H)-ones is reported. All compounds were tested for their influence on melanin synthesis in murine B16 cells. The azepine fragment in thieno[2,3-d]pyrimidin-4(3H)-one skeleton significantly increases the melanin content.

An Isoxazole Chalcone Derivative Enhances Melanogenesis in B16 Melanoma Cells via the Akt/GSK3β/β-Catenin Signaling Pathways

Plants or plant-derived products have been routinely used in several traditional medicine systems for vitiligo treatment. It is well-known that melanogenesis can be promoted by certain flavonoid compounds isolated from the traditional Uyghur medicinal plant, Kaliziri. Therefore, Chalcones, one class of flavonoid compounds, has become an interesting target for the development of anti-vitiligo agents. A series of novel isoxazole chalcone derivatives have been designed, synthesized, and evaluated for biological activities by our group. Among them, derivative 1-(4-((3-phenylisoxazol-5-yl)methoxy)phenyl)-3-phenylprop-2-en-1-one (PMPP) was identified as a potent tyrosinase activator with better activity and lower toxicity than the positive control 8-methoxypsoralen (8-MOP) in this study. Further investigations revealed that Akt and GSK3β were the signaling pathways involved in the hyperpigmentation of PMPP. Overall, these studies may provide a convenient and novel approach for the further development of anti-vitiligo agents.

Hypopigmenting Effects of Brown Algae-Derived Phytochemicals: A Review on Molecular Mechanisms

There is a rapid increase in the demand for natural hypopigmenting agents from marine sources for cosmeceutical and pharmaceutical applications. Currently, marine macroalgae are considered as a safe and effective source of diverse bioactive compounds. Many research groups are exploring marine macroalgae to discover and characterize novel compounds for cosmeceutical, nutraceutical, and pharmaceutical applications. Many types of bioactive secondary metabolites from marine algae, including phlorotannins, sulfated polysaccharides, carotenoids, and meroterpenoids, have already been documented for their potential applications in the pharmaceutical industry. Among these metabolites, phlorotannins from brown algae have been widely screened for their pharmaceutical and hypopigmenting effects. Unfortunately, the majority of these articles did not have detailed investigations on molecular targets, which is critical to fulfilling the criteria for their cosmeceutical and pharmaceutical use. Very recently, a few meroterpenoids have been discovered from Sargassum sp., with the examination of their anti-melanogenic properties and mechanisms. Despite the scarcity of in vivo and clinical investigations of molecular mechanistic events of marine algae-derived hypopigmenting agents, identifying the therapeutic targets and their validation in humans has been a major challenge for future studies. In this review, we focused on available data representing molecular mechanisms underlying hypopigmenting properties of potential marine brown alga-derived compounds.

Isochlorogenic acid A promotes melanin synthesis in B16 cell through the β-catenin signal pathway

Isochlorogenic acid A, also called 3,5-dicaffeoylquinic acid (3,5-diCQA), is a widespread phenolic compound in the plant. Recent studies have shown that it has antioxidant and anti-inflammatory activity. In addition, oxidative stress and inflammation induced by solar ultraviolet radiation is a very significant reason for skin depigmentation. Therefore, in this study, we evaluated the effect of 3,5-diCQA on B16 cells and explored its molecular mechanism. Results showed that 3,5-diCQA upregulated intracellular melanin production in a time- and dose-dependent manner. Tyrosinase (TYR) activity was also increased after treatment with 3,5-diCQA in a dose-dependent manner. Expressions of TYR, TYR-related protein1, TYR-related protein2, and microphthalmia-associated transcription factor were upregulated in a dose-dependent manner after 48 h of treatment with 3,5-diCQA. Results also showed that 3,5-diCQA promoted the phosphorylation of Akt at Thr308 and glycogen synthase kinase-3β at Ser 9. Moreover, 3,5-diCQA increased the content of β-catenin in cell cytoplasm and nucleus by reducing the content of phosphorylated β-catenin (p-β-catenin). All these results suggest that 3,5-diCQA may mediate the acceleration of melanin synthesis by the β-catenin signal pathway.

Synthesis and biological evaluation of furocoumarin derivatives on melanin synthesis in murine B16 cells for the treatment of vitiligo

Furocoumarins, isolated from Psoralen corylifolia L., were found to be the most effective drug in the treatment of vitiligo nowadays. Twenty-five furocoumarin derivatives were thus designed and synthesized in order to improve the melanogenesis in B16 cells for the first time. Among them, twenty-three compounds were more potent than the positive control (8-MOP), the commonly used drug for vitiligo in clinic. Noticeably, compounds 6m (350.5%) and 6p (313.1%) based on the scaffold of 6k (2H-benzofuro[2,3-h]chromen-2-one) were nearly 3-fold stronger than 8-MOP (114.50%). The in vitro melanin synthesis evaluation of these structurally diverse analogues had also led to an outline of structure-activity relationship.