Downregulation of melanogenesis: drug discovery and therapeutic options

Insights into the mechanism of color formation of the freshwater prawn (Macrobrachium rosenbergii) revealed by de novo assembly transcriptome analysis

Body color is an important visual indicator of crustacean quality and plays a major role in consumer acceptability, perceived quality, and the market price of crustaceans. The freshwater prawn (Macrobrachium rosenbergii) has two distinct phenotypic variations, characterized by dark blue and light yellow body colors. However, the underlying mechanisms regulating the body color of M. rosenbergii remain unclear. In this study, the composition of shell color parameters and pigment cells of raw and cooked dark blue and light yellow M. rosenbergii was investigated and the mechanisms associated with body color were elucidated by transcriptome analysis. The results showed significant differences in the raw shells of the dark blue and light yellow M. rosenbergii (L: 26.20 ± 0.53 vs. 29.25 ± 0.45; a: -0.88 ± 0.19 vs. 0.35 ± 0.18; b: 1.73 ± 0.20 vs. 3.46 ± 0.37; dE: 70.33 ± 0.53 vs. 67.34 ± 0.45, respectively, p = 0.000) as well as the cooked shells (L: 58.14 ± 0.81 vs. 55.78 ± 0.55; a: 19.30 ± 0.56 vs. 16.42 ± 0.40; b: 23.60 ± 0.66 vs. 20.30 ± 0.40, respectively, p < 0.05). Transcriptome differential gene analysis obtained 39.02 Gb of raw data and 158,026 unigenes. Comprehensive searches of the SwissProt, Nr, KEGG, Pfam, and KOG databases resulted in successful annotations of 23,902 (33 %), 40,436 (25.59 %), 32,015 (20.26 %), 26,139 (16.54 %), and 22,155 (14.02 %) proteins, respectively. By KEGG pathway analysis, numerous differentially expressed genes were related to pigmentation-related pathways (MAPK signaling pathway, Wnt signaling pathway, melanin production, tyrosine metabolism, and cell-cell communication process). Candidate DEGs that may be involved in body color included apolipoprotein D, crustacyanin, cytochrome P450, and tyrosinase, as verified by quantitative real-time PCR. The results of this study provide useful references to further elucidate the molecular mechanisms of color formation of M. rosenbergii and other crustaceans.

Petanin Potentiated JNK Phosphorylation to Negatively Regulate the ERK/CREB/MITF Signaling Pathway for Anti-Melanogenesis in Zebrafish

Petanin, an acylated anthocyanin from the Solanaceae family, shows potential in tyrosinase inhibitory activity and anti-melanogenic effects; however, its mechanism remains unclear. Therefore, to investigate the underlying mechanism of petanin's anti-melanogenic effects, the enzyme activity, protein expression and mRNA transcription of melanogenic and related signaling pathways in zebrafish using network pharmacology, molecular docking and molecular dynamics simulation were combined for analysis. The results showed that petanin could inhibit tyrosinase activity and melanogenesis, change the distribution and arrangement of melanocytes and the structure of melanosomes, reduce the activities of catalase (CAT) and peroxidase (POD) and enhance the activity of glutathione reductase (GR). It also up-regulated JNK phosphorylation, inhibited ERK/RSK phosphorylation and down-regulated CREB/MITF-related protein expression and mRNA transcription. These results were consistent with the predictions provided through network pharmacology and molecular docking. Thus, petanin could inhibit the activity of tyrosinase and the expression of tyrosinase by inhibiting and negatively regulating the tyrosinase-related signaling pathway ERK/CREB/MITF through p-JNK. In conclusion, petanin is a good tyrosinase inhibitor and anti-melanin natural compound with significant market prospects in melanogenesis-related diseases and skin whitening cosmetics.

Multiplicative Effects of Essential Oils and Other Active Components on Skin Tissue and Skin Cancers

Naturally derived essential oils and their active components are known to possess various properties, ranging from anti-oxidant, anti-inflammatory, anti-bacterial, anti-fungal, and anti-cancer activities. Numerous types of essential oils and active components have been discovered, and their permissive roles have been addressed in various fields. In this comprehensive review, we focused on the roles of essential oils and active components in skin diseases and cancers as discovered over the past three decades. In particular, we opted to highlight the effectiveness of essential oils and their active components in developing strategies against various skin diseases and skin cancers and to describe the effects of the identified essential-oil-derived major components from physiological and pathological perspectives. Overall, this review provides a basis for the development of novel therapies for skin diseases and cancers, especially melanoma.

Integrative pharmacology reveals the mechanisms of Erzhi pills, A traditional Chinese formulation, stimulating melanogenesis

ETHNOPHARMACOLOGICAL RELEVANCE

Erzhi pills (EZP), a traditional Chinese medicine formula prescribed for the treatment of vitiligo, has shown promising efficacy. However, the oral bioactive components and mechanisms underlying the promotion of melanogenesis by EZP remain unclear.

AIM OF THE STUDY

This study aimed to investigate the pharmacological basis and mechanism of EZP in promoting melanogenesis.

MATERIALS AND METHODS

UHPLC-TOF-MS analysis was used to identify absorbed phytochemicals in serum after oral administration of EZP. Network pharmacology methods were used to predict potential targets and pathways involved in the melanogenic activity of EZP, resulting in the construction of a "compound-target-pathway" network. Zebrafish and B16F10 cells were used to evaluate the effects of EZP on tyrosinase activity and melanin content. Western blot and ELISA analyses were used to validate the effects of EZP on melanogenesis-related proteins, including MITF, TYR, CREB, p-CREB, and cAMP.

RESULTS

UHPLC-TOF-MS analysis identified 36 compounds derived from EZP in serum samples. Network pharmacology predictions revealed 89 target proteins associated with the identified compounds and closely related to vitiligo. GO and KEGG analyses indicated the involvement of the cAMP/PKA signaling pathway in the promotion of melanogenesis by EZP. Experimental results showed that EZP increased tyrosinase activity and melanin content in zebrafish and B16F10 cells without inducing toxicity. Western blot and ELISA results suggested that the melanogenic effect of EZP may be related to the activation of the cAMP/PKA signaling pathway. These results confirm the feasibility of combining serum pharmacological and network pharmacological approaches.

CONCLUSIONS

EZP have the potential to increase tyrosinase activity and melanin content in zebrafish and cells possibly through activation of the cAMP/PKA pathway.

(2-Methylbutyryl)shikonin Naturally Occurring Shikonin Derivative Ameliorates the α-MSH-Induced Melanogenesis via ERK1/2 and p38 MAP Kinase-Mediated Down-Regulation of the MITF Transcription Factor

Cutaneous pigmentation is an important phenotypic trait whose regulation, despite recent advances, has yet to be completely elucidated. Melanogenesis, a physiological process of melanin production, is imperative for organism survival as it provides protection against the environmental insults that majorly involve sunlight-induced skin photodamage. However, immoderate melanin synthesis can cause pigmentation disorders associated with a psychosocial impact. In this study, the hypopigmentation effect of (2-methylbutyryl)shikonin, a natural product present in the root extract of Lithospermum erythrorhizon, and the underlying mechanisms responsible for the inhibition of melanin synthesis in α-MSH-stimulated B16F10 cells and C57BL/6J mice was studied. Non-cytotoxic concentrations of (2-methylbutyryl)shikonin significantly repressed cellular tyrosinase activity and melanin synthesis in both in vitro and in vivo models (C57BL/6J mice). (2-Methylbutyryl)shikonin remarkably abolished the protein expression of MITF, tyrosinase, tyrosinase-related protein 1, and tyrosinase-related protein 2, thereby blocking the production of pigment melanin via modulating the phosphorylation status of MAPK proteins, viz., ERK1/2 and p38. In addition, specific inhibition of ERK1/2 attenuated the inhibitory effects of (2-methylbutyryl)shikonin on melanin synthesis, whereas selective inhibition of p38 augmented the inhibitory effect of BSHK on melanin synthesis. Moreover, topical application of (2-methylbutyryl)shikonin on C57BL/6J mouse tails remarkably induced tail depigmentation. In conclusion, with these findings, we, for the first time, report the hypopigmentation effect of (2-methylbutyryl)shikonin via inhibition of cellular tyrosinase enzyme activity, subsequently ameliorating the melanin production, thereby indicating that (2-methylbutyryl)shikonin is a potential natural therapy for hyperpigmentation disorders.

Ginsenoside Rf in wild ginseng adventitious roots extract inhibits melanogenesis via cAMP/PKA and NO/cGMP signalling pathways in α-melanocyte-stimulating hormone-stimulated B16F10 mouse melanoma cells and zebrafish

The scarcity of more effective wild ginseng has severely limited its use, culturing of adventitious roots from wild ginseng were its good substitute. In this study, we found ginsenoside Rf as the special component in adventitious roots extract significantly decreased melanin levels and tyrosinase activity in B16F10 cells and zebrafish, and suppressed the expression of microphthalmia-associated transcription factor and melanogenic enzymes in B16F10 cells. Notably, Rf treatment of B16F10 cells led to reduced cell levels of adenosine cyclic 3', 5'-monophosphate (cAMP), nitric oxide (NO), and guanoside cyclic 3', 5'-monophosphate (cGMP), and reduced activities of adenylate cyclase (AC), protein kinase A (PKA), guanylate cyclase (GC), and protein kinase G (PKG), which suggest Rf anti-melanogenic activity potentially involved inhibition of AC/cAMP/PKA and NO/GC/cGMP/PKG signalling pathway. This work provides experimental basis for skin-lightening effect of wild ginseng adventitious roots and their functional part.

Valorization of biomass polyphenols as potential tyrosinase inhibitors

Tyrosinases (TYRs; EC 1.14.18.1) catalyze two sequential oxidative reactions of the melanin biosynthesis pathway and play an important role in mammalian pigmentation and enzymatic browning of fruit and vegetables. Inhibition of TYR activity is therefore an attractive target for new drugs and/or food ingredients. In addition, increasing evidence suggests that TYR regulation could be a novel target for treatments of cancer and Parkinson's disease. Biomasses, notably industrial byproducts and biowaste, are good sustainable sources of phytochemicals that may be valorized into bioactive compounds including TYR inhibitors. This review presents potential applications of biomass-derived polyphenols targeting TYR inhibition. Insights into structure-activity relationships of several polyphenols and their glycosides are highlighted. Finally, some remarks and perspectives on research into new TYR inhibitors from biomass waste are provided.

Synthesis, in silico modelling, and in vitro biological evaluation of substituted pyrazole derivatives as potential anti-skin cancer, anti-tyrosinase, and antioxidant agents

Twenty-five azole compounds (P1-P25) were synthesised using regioselective base-metal catalysed and microwave-assisted approaches, fully characterised by high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR), and infrared spectra (IR) analyses, and evaluated for anticancer, anti-tyrosinase, and anti-oxidant activities in silico and in vitro. P25 exhibited potent anticancer activity against cells of four skin cancer (SC) lines, with selectivity for melanoma (A375, SK-Mel-28) or non-melanoma (A431, SCC-12) SC cells over non-cancerous HaCaT-keratinocytes. Clonogenic, scratch-wound, and immunoblotting assay data were consistent with anti-proliferative results, expression profiling therewith implicating intrinsic and extrinsic apoptosis activation. In a mushroom tyrosinase inhibition assay, P14 was most potent among the compounds (half-maximal inhibitory concentration where 50% of cells are dead, IC50 15.9 μM), with activity greater than arbutin and kojic acid. Also, P6 exhibited noteworthy free radical-scavenging activity. Furthermore, in silico docking and absorption, distribution, metabolism, excretion, and toxicity (ADMET) simulations predicted prominent-phenotypic actives to engage diverse cancer/hyperpigmentation-related targets with relatively high affinities. Altogether, promising early-stage hits were identified - some with multiple activities - warranting further hit-to-lead optimisation chemistry with further biological evaluations, towards identifying new skin-cancer and skin-pigmentation renormalising agents.

Molecular Docking and Dynamics Simulations of Ammi visnaga L. Constituents as Antimelanogenic, Anti-Inflammatory and Anticoagulant Agents

In this study, anti-melanogenic, anti-inflammatory and anti-coagulant potentials of eighteen selected constituents of Ammi visnaga L. were investigated by Induced Fit Docking (IFD) and molecular dynamic simulation with Schrödinger software. The binding free energies of the selected natural compounds were computed by means of ΔG MM-GBSA studies. Anti-melanogetic activity of the constituent against agaricus bisporus tyrosinase, Priestia megaterium tyrosinase and Homo sapiens tyrosinase were evaluated. The result showed that apiumetin had more negative binding free energy against three tyrosinase enzymes than cognate ligands, tropolone and kojic acid. Docking analysis was also performed to predict the constituents with anti-inflammatory activity against human Tumor necrosis factor, Cyclooxygenase-2, Prostaglandin D2 11-ketoreductase AKR1C3 and Prostaglandin reductase PTGR2. The results showed that pyranocoumarins (visnadin, dihydrosamidin, samidin) have more negative binding free energy against Cyclooxygenase-2 and Prostaglandin D2 11-ketoreductase receptors than cognate drugs, rofecoxib and indomethacin. In addition, docking analysis shows that pyranocoumarins, apiumetin and cimifugin have more negative binding free energy against Vitamin K epoxide reductase than S-warfarin drug, predicting that they have anticoagulant activity. Furthermore, the constituents and their cognate drugs were subjected to 100 ns MD Simulation to predict their stability at the active sites of the enzymes.

New insights into the regulation mechanism of Pacific white shrimp (Litopenaeus vannamei) hepatopancreas under 4-nonylphenol exposure using transcriptome analysis

4-Nonylphenol (4-NP) is one of the common endocrine-disrupting chemicals (EDCs) in estuaries and coastal zones, which can exert detrimental effects on the physiological function of aquatic organisms. However, the molecular response triggered by 4-NP remains largely unknown in Pacific white shrimp (Litopenaeus vannamei). In this study, transcriptomic analysis was performed to investigate the underlying mechanisms of 4-NP toxicity in the hepatopancreas of L. vannamei. Nine RNA-Seq libraries were generated from L. vannamei at 0 h, 24 h, and 48 h following exposure to 4-NP. Compared with 0 h vs 24 h, 962 up- and 463 down-regulated differentially expressed genes (DEGs) were identified, indicating that many genes in L. vannamei were induced to resist adverse circumstances by 4-NP exposure. In contrast, 902 up- and 1027 down-regulated DEGs were revealed in the comparison of 0 h vs 48 h, demonstrating that prolonged exposure to the stress from 4-NP resulted in more inhibited genes. To validate the accuracy of the transcriptome data, eight DEGs were selected for quantitative real-time polymerase chain reaction (qRT-PCR), which were consistent with the RNA-Seq results. Through KEGG pathway enrichment analysis, three specific pathways related to hormonal effects and endocrine function of L. vannamei were enriched significantly, including tyrosine metabolism, insect hormone biosynthesis, and melanogenesis. After 4-NP stress, genes involved in tyrosine metabolism (Tyr) and melanogenesis pathway (AC, CBP, Wnt, Frizzled, Tcf, and Ras) were induced to promote melanin pigment to help shrimp resist adverse environments. In the insect hormone biosynthesis, ALDH, CYP15A1, CYP15A1/C1, and JHE genes were activated to synthesize juvenile hormone (JH), while Spook, Phm, Sad, and CYP18A1 were induced to generate molting hormone. There is an enhanced interaction between the molting hormone and JH, with JH playing a dominant role and maintaining its "classic status quo action". Our study demonstrated that 4-NP exposure led to impairments of biological functions in L. vannamei hepatopancreas. The genes and pathways identified provide novel insights into the molecular mechanisms underlying 4-NP toxicity effects in prawns and enrich the information on the toxicity mechanism of crustaceans in response to EDCs exposure.

Atractylodes lancea rhizome derived exosome-like nanoparticles prevent alpha-melanocyte stimulating hormone-induced melanogenesis in B16-F10 melanoma cells

Aberrant melanin overproduction can significantly impact an individual's appearance and cause mental and psychological distress. Current inhibitors of melanin production exert harmful side effects due to inadequate selectivity; thus a need to develop more selective melanin synthesis inhibitors is necessary. Extracellular vesicles are important agents of intercellular signalling in prokaryotes and eukaryotes. Recently, plant-derived nanoparticles, similar to mammalian exosomes, have attracted attention for their use in health research. In this study, to investigate the potential of plant-derived exosome-like nanoparticles (ELNs) as inhibitors of melanin production, we used hot water to extract ELNs from the rhizome of Atractylodes lancea (A-ELNs). The size of A-ENLs ranged from 34 to 401 nm and carried three microRNA: ath-miR166f, ath-miR162a-5p, and ath-miR162b-5p. These A-ENLs were applied to B16-F10 melanoma cells treated with α-melanocyte-stimulating hormone (α-MSH). After A-ELNs were taken up by B16-F10 cells, their melanin levels were significantly reduced. Furthermore, A-ELNs significantly reduced tyrosinase activity in B16-F10 cells and mRNA expression of microphthalmia-associated transcription factor (Mitf), tyrosinase, tyrosinase-related protein 1, and DOPA chrome tautomerase. These results suggest that A-ELN suppresses melanogenic enzymes expression by downregulating Mitf, thereby inhibiting melanin synthesis. Hence, A-ELN can be developed into a novel topical drug after additional studies and optimization.

Plant-Derived Vesicle-Like Nanoparticles as Promising Biotherapeutic Tools: Present and Future

Extracellular vesicles (EVs) are heterogeneous, phospholipid bilayer-enclosed biological particles that regulate cell communication by molecular cargo delivery and surface signaling. EVs are secreted by almost all living cells, including plant cells. Plant-derived vesicle-like nanoparticles (PDVLNs) is a generic term referring to vesicle-like nanostructure particles isolated from plants. Their low immunogenicity and wide availability make PDVLNs safer and more economical to be developed as therapeutic agents and drug carriers. Accumulating evidence indicates the key roles of PDVLNs in regulating interkingdom crosstalk between humans and plants. PDVLNs are capable of entering the human-body systemand delivering effector molecules to cells that modulate cell-signaling pathways. PDVLNs released by or obtained from plants thus have great influenceon human health and diseases. In this review, the biogenesis, detailed preparation methods, various physical and biochemical characteristics, biosafety, and preservation of PDVLNs are introduced, along with how these characteristics pertain to their biosafety and preservability. The potential applications of PDVLNs on different plant and mammalian diseases and PDVLN research standardization are then systematically discussed.

Microphthalmia-Associated Transcription Factor: A Differentiation Marker in Uveal Melanoma

Microphthalmia-associated transcription factor (MITF) is an important regulator of melanogenesis and melanocyte development. In cutaneous melanoma, MITF loss has been linked to an increased expression of stem cell markers, a shift in epithelial-to-mesenchymal transition (EMT)-related factors, and increased inflammation. We explored the role of MITF in Uveal Melanoma (UM) using a cohort of 64 patients enucleated at the Leiden University Medical Center. We analysed the relation between MITF expression and clinical, histopathological and genetic features of UM, as well as survival. We performed differential gene expression and gene set enrichment analysis using mRNA microarray data, comparing MITF-low with MITF-high UM. MITF expression was lower in heavily pigmented UM than in lightly pigmented UM (p = 0.003), which we confirmed by immunohistochemistry. Furthermore, MITF was significantly lower in UM with monosomy 3/BAP1 loss than in those with disomy 3/no BAP1 loss (p < 0.001) and with 8q gain/amplification 8q (p = 0.02). Spearman correlation analysis showed that a low MITF expression was associated with an increase in inflammatory markers, hallmark pathways involved in inflammation, and epithelial-mesenchymal transition. Similar to the situation in cutaneous melanoma, we propose that MITF loss in UM is related to de-differentiation to a less favourable EMT profile and inflammation.

Targeting Tyrosinase in Hyperpigmentation: Current Status, Limitations and Future Promises

Hyperpigmentation is a common and distressing dermatologic condition. Since tyrosinase (TYR) plays an essential role in melanogenesis, its inhibition is considered a logical approach along with other therapeutic methods to prevent the accumulation of melanin in the skin. Thus, TYR inhibitors are a tempting target as the medicinal and cosmetic active agents of hyperpigmentation disorder. Among TYR inhibitors, hydroquinone is a traditional lightening agent that is commonly used in clinical practice. However, despite good efficacy, prolonged use of hydroquinone is associated with side effects. To overcome these shortcomings, new approaches in targeting TYR and treating hyperpigmentation are desperately requiredessentialneeded. In line with this purpose, several non-hydroquinone lightening agents have been developed and suggested as hydroquinone alternatives. In addition to traditional approaches, nanomedicine and nanotheranostic platforms have been recently proposed in the treatment of hyperpigmentation. In this review, we discuss the available strategies for the management of hyperpigmentation with a focus on TYR inhibition. In addition, alternative treatment options to hydroquinone are discussed. Finally, we present nano-based strategies to improve the therapeutic effect of drugs prescribed to patients with skin disorders.

Natural Melanogenesis Inhibitor, Antioxidant, and Collagen Biosynthesis Stimulator of Phytochemicals in Rice Bran and Husk Extracts from Purple Glutinous Rice (Oryza sativa L. cv. Pieisu 1 CMU) for Cosmetic Application

Oryza sativa L. cv. Pieisu 1 CMU (PES1CMU) has a high anthocyanin content in the colored bran and high phenolic content in the husk. Biologically active compounds in plants are available as dietary supplements and cosmetics. To expand the utilization of natural resources, PES1CMU will be a natural remedy for skin hyperpigmentation and aging. Cell-free tyrosinase inhibition and scavenging assays were used to screen all extracts, including PES1CMU-rice bran oil (RBO), PES1CMU-defatted rice bran (DFRB), and PES1CMU-husk (H). PES1CMU extracts were first examined in IBMX-stimulated B16 cells and H₂O₂-induced fibroblasts. The results exhibited that PES1CMU-DFRB was the most effective inhibitor of mushroom tyrosinase, intracellular melanin production (fold change of 1.11 ± 0.01), and tyrosinase activity (fold change of 1.22 ± 0.10) in IBMX-stimulated B16 cells. Particularly, PES1CMU-DFRB showed a comparable whitening effect to the standard arbutin with no significant difference (p > 0.05). Moreover, PES1CMU-DFRB and PES1CMU-H demonstrated strong scavenging activities. After accelerated cell aging caused by H₂O₂ exposure in fibroblasts, the levels of malondialdehyde production in all PES1CMU-treated fibroblasts were comparable with those of standard l-ascorbic acid (p > 0.05). Besides, PES1CMU-DFRB and PES1CMU-H treatment significantly inhibited collagen degradation against MMP-2 compared to l-ascorbic acid-treated cells (p > 0.05). PES1CMU rice-processing wastes (DFRB and H) could become potential natural sources for dermatocosmetic constituents in skin anti-aging and whitening products.

The Identification and Characteristics of miRNAs Related to Cashmere Fiber Traits in Skin Tissue of Cashmere Goats

microRNAs (miRNAs) are involved in the regulation of biological phenomena by down-regulating the expression of mRNAs. In this study, Liaoning cashmere (LC) goats (n = 6) and Ziwuling black (ZB) goats (n = 6) with different cashmere fiber production performances were selected. We supposed that miRNAs are responsible for the cashmere fiber trait differences. To test the hypothesis, the expression profiles of miRNAs from the skin tissue of the two caprine breeds were compared using small RNA sequencing (RNA-seq). A total of 1293 miRNAs were expressed in the caprine skin samples, including 399 known caprine miRNAs, 691 known species-conserved miRNAs, and 203 novel miRNAs. Compared with ZB goats, 112 up-regulated miRNAs, and 32 down-regulated miRNAs were found in LC goats. The target genes of the differentially expressed miRNAs were remarkably concentrated on some terms and pathways associated with cashmere fiber performance, including binding, cell, cellular protein modification process, and Wnt, Notch, and MAPK signaling pathways. The miRNA-mRNA interaction network found that 14 miRNAs selected may contribute to cashmere fiber traits regulation by targeting functional genes associated with hair follicle activities. The results have reinforced others leading to a solid foundation for further investigation of the influences of individual miRNAs on cashmere fiber traits in cashmere goats.

Cryptochrome 1 activation inhibits melanogenesis and melanosome transport through negative regulation of cAMP/PKA/CREB signaling pathway

Cutaneous pigmentation was recently shown to be an event regulated by clock proteins. Cryptochrome (CRY) is a key protein composing the feedback loop of circadian clock, however, the function of CRY in melanocytes remains unclear. Here, we found that KL001, a synthetic small molecule modulator of CRY1, inhibited melanin synthesis, as well as reduced melanocyte dendrite elongation and melanosome transport. In addition, the dominant role of CRY1 in KL001-induced anti-melanogenesis was revealed by small interfering RNA transfection. Cellular tyrosinase activity and expression level of melanogenic proteins, including tyrosinase, TRP-1, TRP-2, and transport proteins like Rab27a, Cdc42 and Myosin Va induced by α-MSH were remarkably reversed after KL001 treatment. Mechanistically, CRY1 activation inhibited melanogenesis through CREB-dependent downregulation of MITF and CREB phosphorylation was mediated by classical cAMP/PKA pathway. In addition, the other CRY1 activator, KL044 also suppressed cAMP/PKA/CREB pathway and inhibited melanogenesis. Finally, anti-melanogenic efficacy of KL001 was confirmed by determination of melanin contents in UVB-tanning model of brown guinea pigs, which indicated that targeting CRY1 activity, via topical application of small molecule activator, can be utilized therapeutically to manage human pigmentary disorders.

In vivo reduction of age-dependent neuromelanin accumulation mitigates features of Parkinson's disease

Humans accumulate with age the dark-brown pigment neuromelanin inside specific neuronal groups. Neurons with the highest neuromelanin levels are particularly susceptible to degeneration in Parkinson's disease, especially dopaminergic neurons of the substantia nigra, the loss of which leads to characteristic motor Parkinson's disease symptoms. In contrast to humans, neuromelanin does not appear spontaneously in most animals, including rodents, and Parkinson's disease is an exclusively human condition. Using humanized neuromelanin-producing rodents, we recently found that neuromelanin can trigger Parkinson's disease pathology when accumulated above a specific pathogenic threshold. Here, by taking advantage of this newly developed animal model, we assessed whether the intracellular build-up of neuromelanin that occurs with age can be slowed down in vivo to prevent or attenuate Parkinson's disease. Because neuromelanin derives from the oxidation of free cytosolic dopamine, we enhanced dopamine vesicular encapsulation in the substantia nigra of neuromelanin-producing rats by viral vector-mediated overexpression of vesicular monoamine transporter 2 (VMAT2). This strategy reduced the formation of potentially toxic oxidized dopamine species that can convert into neuromelanin and maintained intracellular neuromelanin levels below their pathogenic threshold. Decreased neuromelanin production was associated with an attenuation of Lewy body-like inclusion formation and a long-term preservation of dopamine homeostasis, nigrostriatal neuronal integrity and motor function in these animals. Our results demonstrate the feasibility and therapeutic potential of modulating age-dependent intracellular neuromelanin production in vivo, thereby opening an unexplored path for the treatment of Parkinson's disease and, in a broader sense, brain ageing.

Anti-Melanogenesis Effect of Polysaccharide from Saussurea involucrata on Forskolin-Induced Melanogenesis in B16F10 Melanoma Cells

As one of the prominent medicinal plants listed in the Chinese pharmacopoeia (2020), Saussurea involucrata (Kar. et Kir.) Sch.-Bip was demonstrated to possess various therapeutic effects. In our recent research, we extracted the polysaccharides from S. involucrata (SIP) at optimal conditions and conducted further structure elucidation on the main fraction as well as the confirmation of its possible anti-inflammatory activity. Hence, in this work, we assessed the in vitro antioxidant activity and anti-melanogenesis effects of the crude SIP in forskolin-induced B16F10 melanoma cells. The results show that SIP possessed strong antioxidant activity and was effective in concentration-dependently decreasing melanin formation and inhibiting tyrosinase activity in forskolin-induced B16F10 cells. Based on these results, the inhibitory mechanism of melanogenesis was investigated by measuring Tyrosinase (TYR), Tyrosinase related protein-1 (TRP-1), Tyrosinase related protein-2 (TRP-2), Microphthalmia-associated transcription factor (MITF), cAMP-response element binding protein (CREB), mitogen-activated protein kinases (MAPK) signaling protein members, and β-catenin degradation in forskolin-induced B16F10 cells. The anti-melanogenesis response of SIP might be attributed to the regulation of c-Jun N-terminal kinase (JNK) phosphorylation and β-catenin degradation pathways. These results suggest that polysaccharides from S. involucrata possess a strong anti-melanogenic effect, and thus could be used as a high-value natural material for skin whitening in cosmeceutical industries.

Anserine/Carnosine-Rich Extract from Thai Native Chicken Suppresses Melanogenesis via Activation of ERK Signaling Pathway

Skin hyperpigmentation is an aesthetic problem that leads to psychosocial issues. Thus, skin whitening agents from agro- and poultry-industrial co-products are considered high economic value ingredients of interest for sustainable application. Therefore, this study aimed to determine the cosmeceutical potential of anserine/carnosine-rich chicken extract (ACCE) from the Thai native chicken Pradu Hang Dam Mor Kor 55 (PD) meat. The chemical composition was identified and quantified using the HPLC-UV method. Then, the antioxidation potential of the extract was compared to that of L-anserine and L-carnosine, using 1,1-diphenyl-2-picrylhydrazyl assay and shikonin-induced production of reactive oxygen species in CCD-986Sk cell models, and the anti-melanogenesis effect in the MNT-1 melanoma cell line model was investigated. Furthermore, related mechanisms were identified using colorimetric tyrosinase assay and the Western blot technique. The ACCE was composed of L-anserine and L-carnosine as two major constituents. In a dose-dependent manner, ACCE, L-anserine, and L-carnosine manifested significant antioxidation potential and significant reduction of melanin production. Activation of the extracellular signal-regulated kinase (ERK) signaling pathway and inhibition of tyrosinase activity of ACCE were demonstrated as the mechanisms of the anti-melanogenesis effect. In conclusion, ACCE has been revealed as a potential cosmeceutical agent due to its antioxidation and anti-melanogenic activity in association with L-anserine and L-carnosine composition and biomolecular regulating ability. Therefore, further studies and development should be considered to support the utilization of anserine/carnosine-rich chicken extract in the cosmetic industry for economic value creation and sustainability.

Pouteria macrophylla Fruit Extract Microemulsion for Cutaneous Depigmentation: Evaluation Using a 3D Pigmented Skin Model

Here, we verify the depigmenting action of Pouteria macrophylla fruit extract (EXT), incorporate it into a safe topical microemulsion and assess its effectiveness in a 3D pigmented skin model. Melanocytes-B16F10- were used to assess the EXT effects on cell viability, melanin synthesis, and melanin synthesis-related gene transcription factor expression, which demonstrated a 32% and 50% reduction of intra and extracellular melanin content, respectively. The developed microemulsion was composed of Cremophor EL^®/Span 80 4:1 (w/w), ethyl oleate, and pH 4.5 HEPES buffer and had an average droplet size of 40 nm (PdI 0.40 ± 0.07). Skin irritation test with reconstituted epidermis (Skin Ethic RHE^TM) showed that the formulation is non-irritating. Tyrosinase inhibition was maintained after skin permeation in vitro, in which microemulsion showed twice the inhibition of the conventional emulsion (20.7 ± 2.2% and 10.7 ± 2.4%, respectively). The depigmenting effect of the microemulsion was finally confirmed in a 3D culture model of pigmented skin, in which histological analysis showed a more pronounced effect than a commercial depigmenting formulation. In conclusion, the developed microemulsion is a promising safe formulation for the administration of cutite fruit extract, which showed remarkable depigmenting potential compared to a commercial formulation.

Mechanisms of ultraviolet-induced melasma formation: A review

Melasma, a pigmentation disorder, commonly occurs in exposed skin areas and can be attributed to several factors. Ultraviolet radiation (UVR) is the primary factor that induces and aggravates melasma. Considering gene expression, exposed skin areas experience abnormal gene expression, involving melanin metabolism, oxidative stress, impaired skin barrier function, and abnormal composition of nerve factors. From a histological perspective, UVR can cause basement membrane collapse, melanocyte sinking, and disorders of skin lipid metabolism. Emerging therapies have focused on these pathological alterations in melasma, including platelet-rich plasma, mesotherapy, and phytochemicals. Understanding the role of UVR in the development of melasma can facilitate early prevention and highlight the future direction of melasma treatment.

Study of Novel Furocoumarin Derivatives on Anti-Vitiligo Activity, Molecular Docking and Mechanism of Action

Vitiligo is a common chronic dermatological abnormality that afflicts tens of millions of people. Furocoumarins isolated from Uygur traditional medicinal material Psoralen corylifolia L. have been proven to be highly effective for the treatment of vitiligo. Although many furocoumarin derivatives with anti-vitiligo activity have been synthesized, their targets with respect to the disease are still ambiguous. Fortunately, the JAKs were identified as potential targets for the disease and its inhibitors have been proved to be effective in the treatment of vitiligo in many clinical trials. Thus, sixty-five benzene sulfonate and benzoate derivatives of furocoumarins (7a–7ad, 8a–8ag) with superior anti-vitiligo activity targeting JAKs were designed and synthesized based on preliminary research. The SAR was characterized after the anti-vitiligo-activity evaluation in B16 cells. Twenty-two derivatives showed more potent effects on melanin synthesis in B16 cells than the positive control (8-MOP). Among them, compounds 7y and 8 not only could increase melanin content, but they also improved the catecholase activity of tyrosinase in a concentration-dependent manner. The docking studies indicated that they were able to interact with amino acid residues in JAK1 and JAK2 via hydrogen bonds. Furthermore, candidate 8 showed a moderate inhibition of CXCL−10, which plays an important role in JAK–STAT signaling. The RT-PCR and Western blotting analyses illustrated that compounds 7y and 8 promoted melanogenesis by activating the p38 MAPK and Akt/GSK-3β/β-catenin pathways, as well as increasing the expressions of the MITF and tyrosinase-family genes. Finally, furocoumarin derivative 8 was recognized as a promising candidate for the fight against the disease and worthy of further research in vivo.

Design of melanogenesis regulatory peptides derived from phycocyanin of the microalgae Spirulina platensis

Pigmentation issues are common conditions associated with excessive or insufficient production of melanin. Recently peptides are investigated to discover novel melanogenesis regulators as low molecular weight compounds to regulate skin pigmentation. In this study, an internal library of peptides obtained through in silico enzymatic digestion of phycocyanin from microalgae S. platensis was tested to apprehend their anti-melanogenic effects. Seven peptides were investigated for their inhibitory potential against mushroom and B16-F10 murine tyrosinase enzymes. According to the results, P5 (SPSWY) and P7 (AADQRGKDKCARDIGY) were effective in lowering the activity of mushroom and B16-F10 tyrosinases. P5 was the most potent (IC₅₀ value, 12.1 µM) in mushroom which was followed by P2 (MAACLR, 86.9 µM). Although the peptides were particularly powerful in inhibiting monophenolase activity, only moderate inhibition was observed for diphenolase activity in mushroom tyrosinase assay. Apart from tyrosinase inhibition, P2 and P3 (RCLNGRL) were efficient DPPH radical scavengers at low concentrations (IC₅₀ < 200 µM). In the mammalian assay system, P5 and P7 were noticeably effective to decrease tyrosinase enzyme activity with IC₅₀ values of 48.9 and 34.2 µM, respectively. However, although P4 (RYVTYAVF) was a potent mushroom tyrosinase inhibitor, it increased melanin synthesis up to 3-fold in B16-F10 cells. The results indicate that C-terminal tyrosine residue is important for tyrosinase inhibition. This study shows, for the first time, that microalgae proteins can be regarded as sources for melanogenesis regulation.

Keratinocytes take part in the regulation of substance P in melanogenesis through the HPA axis

BACKGROUND

Clinical findings have shown that skin depigmentation disorder such as vitiligo may be closely associated with the release of central and peripheral substance P (SP) resulted from chronic psychological stress or sudden mental blow. But the regulatory role of SP and its receptor, tachykinin receptor in the pathogenesis of vitiligo is unclear.

OBJECTIVES

To investigate the function and mechanism of SP in melanogenesis.

METHODS

The chronic mental stress was used to explore the intrinsic association between psychological factors, SP and melanogenesis disorder. The effect of SP on melanogenesis through hypothalamic pituitary adrenocortical (HPA) axis was studied by skin culture in vitro. The conditioned medium experiment demonstrated the indirect effect of SP on melanogenesis of B16F10 cells through HaCaT cells. The ability to produce melanin was evaluated by detecting melanin and tyrosinase activity. qRT-PCR, western blotting and immunohistochemistry were used to detect the expression of related genes and proteins in melanogenesis and HPA axis.

RESULTS

Increased SP expression and reduction of melanogenesis in the skin of mice were observed under mental stress. Melanogenesis was suppressed in the cultured human skin treated with SP due to the down-regulation of melanin-related proteins and HPA axis genes. The melanogenesis of B16F10 cells was inhibited by the conditioned medium of HaCaT cells treated with SP.

CONCLUSIONS

Overall, these results indicate that excess SP originated from mental stress interferes with melanogenesis through keratinocytes in the skin. The HPA axis is the key downstream to perceive the SP signaling and furtherly regulate the melanogenesis.

Spreading of Dangerous Skin-Lightening Products as a Result of Colourism: A Review

The use of bleaching products can have a medical or cosmetic purpose; in the latter case, skin whitening is most widespread in countries where darker skin tones prevail and can be driven by psychosocial, cultural and economic reasons. Skin-whitening products containing highly toxic active ingredients (in particular mercury derivatives, hydroquinone and corticosteroids) are easily found on the market; the use of these depigmenting agents can be followed by a variety of adverse effects, with very serious and sometimes fatal complications, and is currently an emerging health concern in many countries. This article concisely discusses the reasons for the current prevalence of skin lightening products and provides an overview of the skin lightening agents that pose a threat to human health. The review also reports market surveillance data on the circulation of banned skin lighteners in Europe, obtained through the Safety Gate system.

Melanogenic effect of dersimelagon (MT-7117), a novel oral melanocortin 1 receptor agonist

Background

The activation of melanocortin 1 receptor (MC1R) on melanocytes stimulates the production of eumelanin. A tridecapeptide α melanocyte‐stimulating hormone (αMSH) is known to induce skin pigmentation.

Objectives

We characterised the properties of a novel oral MC1R agonist dersimelagon (MT‐7117) with respect to its specific binding to MC1R, downstream signalling and eumelanin production in experimental models.

Methods

The competitive binding and production of intracellular cyclic adenosine 3′, 5′‐monophosphate in cells expressing recombinant melanocortin receptors were examined. A mouse melanoma cell line B16F1 was used for the evaluation of in vitro melanin production. The in vitro activity of MT‐7117 was determined with αMSH and [Nle⁴, D‐Phe⁷]‐αMSH (NDP‐αMSH) as reference comparators. The change of coat colour and skin pigmentation were evaluated after repeat administration of MT‐7117 by oral gavage to C57BL/6J‐A^y/+ mice and cynomolgus monkeys, respectively.

Results

MT‐7117 showed the highest affinity for human MC1R compared to the other melanocortin receptors evaluated and agonistic activity for human, cynomolgus monkey and mouse MC1R, with EC₅₀ values in the nanomolar range. In B16F1 cells, MT‐7117 increased melanin production in a concentration‐dependent manner. In vivo, MT‐7117 (≥0.3 mg/kg/day p.o.) significantly induced coat colour darkening in mice. MT‐7117 (≥1 mg/kg/day p.o.) induced significant skin pigmentation in monkeys and complete reversibility was observed after cessation of its administration.

Conclusions

MT‐7117 is a novel oral MC1R agonist that induces melanogenesis in vitro and in vivo, suggesting its potential application for the prevention of phototoxic reactions in patients with photodermatoses, such as erythropoietic protoporphyria and X‐linked protoporphyria.

A review of the ethnopharmacology, phytochemistry and pharmacology of Cynanchumatratum

ETHNOPHARMACOLOGICAL RELEVANCE

The dried roots and rhizomes of Cynanchum atratum Bunge is named 'Baiwei' according to traditional Chinese medicine theory. It is also named Cynanchi atrati Radix in Chinese Pharmacopoeia. Cynanchi atrati Radix is famous for its medicinal value of clearing away heat, relieving drenching, detoxifying and treating abscesses. It was commonly used in some Asian countries for the treatment of fever, vasoconstrictive syncope, lymphangitis and other diseases, obviously due to the effect of C₂₁ steroidal glycosides.

THE AIM OF THE REVIEW

The review concentrates on the botany, ethnopharmacology, phytochemistry, pharmacology and toxicology of Cynanchum atratum. We also discuss expectations for prospective research and implementation of this herb.

MATERIALS AND METHODS

Relevant information about C. atratum was gained from ancient books and records, Doctoral and master's Theses, Science Direct, Pubmed, Wiley, CNKI, WanFang DATA, Google Scholar and other domestic and foreign literature. Some electronic databases have been included.

RESULTS

As a member of the Apocynaceae family, C. atratum possesses its up-and-coming biological characteristics. It is widely reported for treating of postpartum fatigue, vomiting, urine drops, nephritis, urinary tract infection, edema, bronchitis and rheumatic low back pain. By now, over 100 compounds have been identified from C. atratum, including C₂₁ steroidal glycosides, acetophenones, alkaloids, volatile oil and other ingredients. Activities such as anti-inflammatory, anti-tumor, anti-virus, antibacterial, anti-forgetful and others have been corroborated in vivo and in vitro. In addition, many of the active ingredients, such as Cynatratoside A, Cynanversicoside A, B, D, G, p-hydroxyacetophenone, 2,4-dihydroxyacetophenone and some volatile oils have been used as quality markers.

CONCLUSION

All kinds of research conducted on C.atratum, especially in field of ethnopharmacological use, phytochemicals and pharmacology have been reviewed. The herb has been used over the years in treating nephritis, urinary tract infection, bronchitis and rheumatic lumbocrural pain. Many studies have been carried out to identify compounds that play a leading role in drug activity. However, the mechanism of drug therapy remains unclear. The evidence used to prove the quality standard of medicinal materials is obviously inadequate. Besides, safety evaluation is necessary for clinical medication. Similarly, the separation of steroidal saponins and the development of new drugs will also need further discussion.

Effect of Grass Carp Scale Collagen Peptide FTGML on cAMP-PI3K/Akt and MAPK Signaling Pathways in B16F10 Melanoma Cells and Correlation between Anti-Melanin and Antioxidant Properties

Peptide Phe-Thr-Gly-Met-Leu (FTGML) is a bioactive oligopeptide with tyrosinase inhibitory activity derived from gelatin hydrolysate of grass carp scales. Previous studies have shown that FTGML addition can effectively inhibit mushroom tyrosinase activity in vitro, and also has some effect on the inhibition of melanogenesis in zebrafish in vivo, but the underlying mechanism is not fully understood. In this study, we used FTGML to treat B16F10 melanoma cells, and found a significant inhibition of tyrosinase activity and melanin synthesis. Interestingly, the treatment showed a strong correlation between antioxidant activity and anti-melanin, which was associated with FTGML reducing the involvement of reactive oxygen species in melanin synthesis. Furthermore, FTGML reduced melanogenesis in B16F10 cells by downregulating the cAMP-PI3K/Akt and MAPK pathways (p38 and JNK). These results suggested that FTGML can reduce melanin production in mouse B16F10 melanoma cells through multiple pathways.

Chrysoeriol Enhances Melanogenesis in B16F10 Cells Through the Modulation of the MAPK, AKT, PKA, and Wnt/β-Catenin Signaling Pathways

Chrysoeriol is a 3′-O-methoxy flavone, chemically a derivative of luteolin, which is commonly found across the plant kingdom. Chrysoeriol is of great scientific interest because of its promising anti-inflammatory, anti-cancer, antioxidative, anti-lipase, anti-xanthin oxidase, and antimicrobial activities against multidrug-resistant (MDR) bacterial pathogens; however, its effects on melanogenesis have not yet been elucidated. Here, we report a novel effect of chrysoeriol on melanogenesis in B16F10 cells. Chrysoeriol treatment significantly increased the expression of the melanogenic enzymes tyrosinase (TRY), tyrosinase-related protein-1 (TRP-1), and TRP-2 and upregulated the expression of microphthalmia-associated transcription factor (MITF) in a concentration-dependent manner. Furthermore, chrysoeriol suppressed the phosphorylation of extracellular signal-regulated kinase (ERK) and protein kinase B (AKT) in a concentration-dependent manner. In addition, chrysoeriol treatment increased the phosphorylation of p38 mitogen-activated protein kinase (MAPK), glycogen synthase kinase (GSK)-3β, β-catenin, and protein kinase A (PKA) and decreased the production of β-catenin, which is involved in the transcriptional activation of MITF in melanogenesis. Finally, the structure–activity relationship (SAR) of chrysoeriol and its derivatives, including luteolin and apigenin, with regard to their melanin inhibitory activity was also investigated; we identified the significance of the 4′-OH group and C-3′ methoxylation in melanogenesis. Together, these findings indicate that chrysoeriol promotes melanogenesis in B16F10 cells by upregulating the expression of melanogenic enzymes through the MAPK, phosphatidylinositol 3-kinase (PI3K)/AKT, PKA, and Wnt/β-catenin signaling pathways; thus, chrysoeriol may be used as a cosmetic ingredient to promote melanogenesis or as a therapeutic agent against hypopigmentation disorders.

Discovery of small-molecule modulators of melanogenesis by docking-based virtual screening

Background: Vitiligo is a relatively common depigmenting skin disorder. UV light stimulation is often used to obtain repigmentation. Wnt signaling regulates melanocyte differentiation, and expression of TYR is upregulated in narrow-band UVB-treated epidermis. Manipulation of these two pathways by drugs could serve as one of the therapeutic approaches for durable repigmentation. Methods and results: CD9 was identified as a novel TYR activator by virtual screening and bioactivity assay. CD9 activated the Wnt signaling pathway through triggering translocation of β-catenin from cytoplasm to nucleus. Conclusion: The pathogenesis of vitiligo is complicated and varies with each individual, so combination therapy may be much more suitable for treatment of vitiligo. CD9 could synergize with other anti-inflammatory compounds or autoimmune suppressors to shorten repigmentation time and improve efficacy.

Attenuation Effect of Radiofrequency Irradiation on UV-B-Induced Skin Pigmentation by Decreasing Melanin Synthesis and through Upregulation of Heat Shock Protein 70

Excess melanin deposition in the skin causes cosmetic problems. HSP70 upregulation decreases microphthalmia-associated transcription factor (MITF) expression, which eventually decreases tyrosinase activity and melanogenesis. Ultraviolet (UV) radiation upregulates p53, which increases the melanocortin receptor (MC1R) and MITF. Furthermore, HSP70 decreases p53 and radiofrequency irradiation (RF) increases HSP70. We evaluated whether RF increased HSP70 and decreased p53, consequently decreasing the MITF/tyrosinase pathway and melanogenesis in UV-B radiated animal skin. Various RF combinations with 50, 100, and 150 ms and 5, 10, and 15 W were performed on the UV-B radiated mouse skin every 2 d for 28 d. When RF was performed with 100 ms/10 W, melanin deposition, evaluated by Fontana–Masson staining, decreased without skin crust formation in the UV-B radiated skin. Thus, we evaluated the effect of RF on decreasing melanogenesis in the HEMn and UV-B radiated skin at a setting of 100 ms/10 W. HSP70 expression was decreased in the UV-B radiated skin but was increased by RF. The expression of p53, MC1R, and MITF increased in the UV-B radiated skin but was decreased by RF. The expression of p53, MC1R, and MITF increased in the α-MSH treated HEMn but was decreased by RF. The decreasing effects of RF on p53, MC1R, CREB and MITF were higher than those of HSP70-overexpressed HEMn. The decreasing effect of RF on p53, MC1R, CREB, and MITF disappeared in the HSP70-silenced HEMn. MC1R, CREB, and MITF were not significantly decreased by the p53 inhibitor in α-MSH treated HEMn. RF induced a greater decrease in MC1R, CREB, and MITF than the p53 inhibitor. Therefore, RF may have decreased melanin synthesis by increasing HSP70 and decreasing p53, thus decreasing MC1R/CREB/MITF and tyrosinase activity.

The Inhibitory Effect of Curcumin Derivative J147 on Melanogenesis and Melanosome Transport by Facilitating ERK-Mediated MITF Degradation

The therapeutic use of curcumin and chemically modified curcumin (CMC) for suppressing melanogenesis and tyrosinase activity have been recognized. J147 is a modified version of curcumin with superior bioavailability and stability. However, there is no report about the effects of J147 on pigmentation in vitro and in vivo. In our studies, we investigated the hypopigmentary effects of J147 treatment on melanocytes and explored the underlying mechanism. The present studies suggested that J147 suppressed both basal and α-MSH-induced melanogenesis, as well as decreased melanocyte dendricity extension and melanosome transport. J147 played these roles mainly by activating the extracellular signal-regulated protein kinase (ERK) pathway. Once activated, it resulted in MITF degradation and further down-regulated the expression of tyrosinase, TRP-1, TRP-2, Myosin Va, Rab27a and Cdc42, ultimately inhibited melanin synthesis and melanosome transport. Furthermore, the hypopigmentary effects of J147 were demonstrated in vivo in a zebrafish model and UVB-induced hyperpigmentation model in brown guinea pigs. Our findings also suggested that J147 exhibited no cytotoxicity in vitro and in vivo. Taken together, these data confirmed that J147 may prove quite useful as a safer natural skin-whitening agent.

Di (Isoquinolin-1-Yl) Sulfane (DIQS) Inhibits Melaninogenesis by Modulating PKA/CREB and MAPK Signaling Pathways

The novel synthetic compound Di (isoquinolin-1-yl) sulfane (DIQS) was identified by zebrafish larva screening during the development of an agent to inhibit abnormal hyperpigmentation. In this study, we investigated the inhibitory effect of DIQS on melanogenesis and its underlying mechanism. DIQS inhibited melanin production and tyrosinase activity in B16F10 cells stimulated with α-melanocyte-stimulating hormone (α-MSH), as well as zebrafish embryos and reconstituted human skin tissue containing melanocytes. DIQS decreased the mRNA and protein expression of microphthalmia-associated transcription factor (MITF) and tyrosinase at a concentration of 10 μM. DIQS also inhibited the phosphorylation of cAMP response element-binding protein (CREB) and p-p38 and p-JNK stimulated by α-MSH. These results suggest that DIQS attenuates hyperpigmentation via inhibition of the cAMP/PKA/CREB/MITF/tyrosinase axis and MAPK pathways. Liquid chromatography–tandem mass spectrometry analysis revealed that DIQS blocked the conversion of tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA) in zebrafish embryos. Finally, we confirmed that DIQS was non-toxic in reconstituted human tissues such as the epidermis, used to test skin sensitization, and the cornea, used to test eye irritation. In summary, the results of this study suggest the potential of DIQS as a small-molecule agent for skin-whitening cosmetics and the treatment of hyperpigmentation disorders without biological toxicity.

Unravelling Anti-Melanogenic Potency of Edible Mushrooms Laetiporus sulphureus and Agaricus silvaticus In Vivo Using the Zebrafish Model

Severe drawbacks associated with the topical use of depigmenting agents in treatments of skin hyperigmentations impose a great demand for novel, effective, and safe melanogenesis inhibitors. Edible and medicinal mushrooms, known for numerous health-promoting properties, represent a rich reservoir of anti-melanogenic compounds, with the potential to be applied in preventing excessive skin pigmentation. Herein, using zebrafish (Danio rerio) as a preclinical animal model, we have demonstrated that ethanol extract of Laetiporus sulphureus (LSE) and Agaricus silvaticus (ASE) are not toxic at high doses up to 400-500 µg/mL while effectively inhibit melanogenesis in a dose-dependent manner. At depigmenting doses, the explored extracts showed no adverse effects on zebrafish embryos melanocytes. Even more, they did not provoke inflammation or neutropenia when applied at the highest dose ensuring almost complete the cells depigmentation. Since LSE and ASE have demonstrated significantly higher the therapeutic potential than kojic acid and hydroquinone, two well-known depigmenting agents, overall results of this study strongly suggest that the explored mushrooms extracts could be used as efficient and safe topical agents in treatments of skin hyperpigmentation disorders.

Design, synthesis, and biological evaluation of symmetrical azine derivatives as novel tyrosinase inhibitors

A series of symmetrical azine derivatives containing different substituted benzyl moieties were designed, synthesized, and evaluated for their inhibitory activity against tyrosinase. The results showed that compounds 3e, 3f, 3h, 3i, 3j, and 3k possess effective tyrosinase inhibition with IC₅₀ values ranging from 7.30 μM to 62.60 μM. Particularly, compounds 3f displayed around three-fold improvement in the potency (IC₅₀ = 7.30 ± 1.15 μM) compared to that of kojic acid (IC₅₀ = 20.24 ± 2.28 μM) as the positive control. Kinetic study of compound 3f confirmed uncompetitive inhibitory activity towards tyrosinase indicating that it can bind to enzyme–substrate complex. Next, molecular docking analysis was performed to study the interactions and binding mode of the most potent compound 3f in the tyrosinase active site. Besides, the cytotoxicity of 3f, as well as its potency to reduce the melanin content were also measured on invasive melanoma B16F10 cell line. Also, 3f exhibited above 82% cell viability in the A375 cell line at 10 µM. Consequently, compounds 3f could be introduced as a potent tyrosinase inhibitor that might be a promising candidate in the cosmetics, medicine, and food industry.

Human amniotic stem cells-derived exosmal miR-181a-5p and miR-199a inhibit melanogenesis and promote melanosome degradation in skin hyperpigmentation, respectively

BACKGROUND

Hyperpigmentation of skin is caused by an imbalance between the melanosome/melanin synthesis in melanocytes and the melanosome/melanin degradation in keratinocytes. Although studies showed that stem cells play a role in hypopigmentation, the underlying mechanisms are far not elucidated. Human amniotic stem cells (hASCs) including human amniotic mesenchymal stem cells (hAMSCs) and human amniotic epithelial stem cells (hAESCs) were considered to be a promising cell source for stem cells-based therapy of many diseases clinically due to their pluripotent potential, no tumorigenesis and immunogenicity, no ethical issues, and potent paracrine effects. Here, we reported that both hASCs and their conditional medium (CM) had a potent anti-hyperpigmentation in skin in vivo and in vitro.

METHODS

hAESCs and hAMSCs were identified by RT-PCR, flow cytometric analysis and immunofluorescence. Effects of hASCs and hASC-CM on pigmentation were evaluated in B16F10 cells stimulated with α-melanocyte-stimulating hormone (α-MSH), and mouse ears or human skin substitutes treated with ultraviolet radiation B (UVB). Expressions of the key proteins related with melanogenesis and autophagic flux were detected by western blot in B16F10 cells for further exploring the effects and the underlying mechanisms of hAESC-CM and hAMSC-CM on melanogenesis and melanosome degradation. The hAMSCs exosomes-derived miRNAs were determined by sequencing. RT-PCR, western blot, melanin content analysis and luciferase activity assay were used to determine the hypopigmentation of miR-181a-5p and miR-199a.

RESULTS

In our study, we observed that both hASCs and their CM significantly alleviated the α-MSH in B16F10 cells or UVB-induced hyperpigmentation in mouse ears or human skin substitutes by suppressing melanin synthesis and promoting melanosome degradation in vivo and in vitro. Furthermore, we demonstrated that miR-181a-5p and miR-199a derived from hASCs exosomes remarkably inhibited melanogenesis by suppressing MITF (microphthalmia-associated transcription factor) which is a master regulator for governing melanogenesis and promoting melanosome degradation through activating autophagy, respectively.

CONCLUSIONS

Our studies provided strong evidence that the conditional medium and exosomes derived from hAMSCs inhibit skin hyperpigmentation by suppressing melanogenesis and promoting melanosome degradation, indicating that the hASCs exosomes or their released microRNAs might be as reagents for cell-free therapy in hyperpigmented disorders clinically.

The anti-melanogenic effects of 3-O-ethyl ascorbic acid via Nrf2-mediated α-MSH inhibition in UVA-irradiated keratinocytes and autophagy induction in melanocytes

3-O-ethyl ascorbic acid (EAA) is an ether-derivative of ascorbic acid, known to inhibit tyrosinase activity, and is widely used in skincare formulations. Nevertheless, the molecular mechanisms underlying the EAA's effects are poorly understood. Here, the anti-melanogenic activity of EAA was demonstrated through Nrf2-mediated α-MSH inhibition in UVA-irradiated keratinocytes (HaCaT) and autophagy induction and inhibition of α-MSH-stimulated melanogenesis in melanocytes (B16F10). EAA pretreatment increased the HaCaT cell viability but suppressed ROS-mediated p53/POMC/α-MSH pathways in UVA-irradiated cells. Further, the conditioned medium from EAA-pretreated and UVA-irradiated HaCaT cells suppressed the MITF-CREB-tyrosinase pathways leading to the inhibition of melanin synthesis in B16F10 cells. EAA treatment increased nuclear Nrf2 translocation via the p38, PKC, and ROS pathways leading to HO-1, γ-GCLC, and NQO-1 antioxidant expression in HaCaT cells. However, Nrf2 silencing reduced the EAA-mediated anti-melanogenic activity, evidenced by impaired antioxidant gene expression and uncontrolled ROS (H₂0₂) generation following UVA irradiation. In B16F10 cells, EAA-induced autophagy was shown by enhanced LC3-II levels, AVO formation, Beclin-1 upregulation, and activation of p62/SQSTM1. Further, EAA-induced anti-melanogenic activity was substantially decreased in autophagy inhibitor (3-MA) pretreated or LC3 knockdown B16F10 cells. Notably, transmission electron microscopy data showed increased melanosome-engulfing autophagosomes in EAA-treated B16F10 cells. Moreover, EAA also down-regulated MC1R, TRP-1/-2, tyrosinase expressions, and melanin synthesis by suppressing the cAMP-CREB-mediated MITF expression in B16F10 cells stimulated with α-MSH. In vivo studies on the zebrafish model further confirmed that EAA inhibited tyrosinase expression/activity and endogenous pigmentation. In conclusion, 3-O-ethyl ascorbic acid is an effective skin-whitening agent and could be used as a topical agent for cosmetic purposes.

Spectrophotometric Assays for Sensing Tyrosinase Activity and Their Applications

Tyrosinase (TYR, E.C. 1.14.18.1), a critical enzyme participating in melanogenesis, catalyzes the first two steps in melanin biosynthesis including the ortho-hydroxylation of L-tyrosine and the oxidation of L-DOPA. Previous pharmacological investigations have revealed that an abnormal level of TYR is tightly associated with various dermatoses, including albinism, age spots, and malignant melanoma. TYR inhibitors can partially block the formation of pigment, which are always used for improving skin tone and treating dermatoses. The practical and reliable assays for monitoring TYR activity levels are very useful for both disease diagnosis and drug discovery. This review comprehensively summarizes structural and enzymatic characteristics, catalytic mechanism and substrate preference of TYR, as well as the recent advances in biochemical assays for sensing TYR activity and their biomedical applications. The design strategies of various TYR substrates, alongside with several lists of all reported biochemical assays for sensing TYR including analytical conditions and kinetic parameters, are presented for the first time. Additionally, the biomedical applications and future perspectives of these optical assays are also highlighted. The information and knowledge presented in this review offer a group of practical and reliable assays and imaging tools for sensing TYR activities in complex biological systems, which strongly facilitates high-throughput screening TYR inhibitors and further investigations on the relevance of TYR to human diseases.

Recent advances in the design and discovery of synthetic tyrosinase inhibitors

Tyrosinase is a copper-containing metalloenzyme that is responsible for the rate-limiting catalytic step in the melanin biosynthesis and enzymatic browning. As a promising target, tyrosinase inhibitors can be used as skin whitening agents and food preservatives, thus having broad potential in the fields of food, cosmetics, agriculture and medicine. From 2015 to 2020, numerous synthetic inhibitors of tyrosinase have been developed to overcome the challenges of low efficacy and side effects. This review summarizes the enzyme structure and biological functions of tyrosinase and demonstrates the recent advances of synthetic tyrosinase inhibitors from the perspective of medicinal chemistry, providing a better understanding of the catalytic mechanisms and more effective tyrosinase inhibitors.

Evaluation of Fatty Acid Compositions, Antioxidant, and Pharmacological Activities of Pumpkin (Cucurbita moschata) Seed Oil from Aqueous Enzymatic Extraction

Pumpkin seed oil is a by-product, abundant in nutrients and bioactive components that promote several health benefits. This study aimed to compare chemical compositions, antioxidant, and pharmacological activities of pumpkin seed oils extracted from Cucurbita moschata Duch. Ex Poir. (PSO1) and Cucurbita moschata (Japanese pumpkin) (PSO2) by aqueous enzymatic extraction. An enzyme mixture consisting of pectinase, cellulase, and protease (1:1:1) was used in the enzymatic extraction process. Fatty acid composition of the oils was determined using fatty acid methyl ester/gas chromatographic-mass spectrometry. Antioxidant activity assays were measured by using stable free radical diphenylpicrylhydrazyl, radical cation 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate, ferric reducing/antioxidant power, and ferric thiocyanate assay. Inhibition of enzymes involving skin aging and whitening process was investigated. Linoleic acid was a major component of all pumpkin seed oils. Additionally, there was also a significant amount of oleic acid, palmitic acid, and stearic acid detected. PSO2 possessed the highest antioxidant activities compared to PSO1 and commercial pumpkin seed oils (COM1 and COM2). Both PSO1 and PSO2 exhibited higher inhibitory effects on hyaluronidase, collagenase, and tyrosinase than the commercials. Therefore, aqueous enzymatic extraction could yield pumpkin seed oils with higher antioxidant, anti-aging, and whitening activities. This is beneficial for further pharmacological studies and can be used as a functional food for skin benefits.

Oxidative stress in the skin: Impact and related protection

Skin, our first interface to the external environment, is subjected to oxidative stress caused by a variety of factors such as solar ultraviolet, infrared and visible light, environmental pollution, including ozone and particulate matters, and psychological stress. Excessive reactive species, including reactive oxygen species and reactive nitrogen species, exacerbate skin pigmentation and aging, which further lead to skin tone unevenness, pigmentary disorder, skin roughness and wrinkles. Besides these, skin microbiota are also a very important factor ensuring the proper functions of skin. While environmental factors such as UV and pollutants impact skin microbiota compositions, skin dysbiosis results in various skin conditions. In this review, we summarize the generation of oxidative stress from exogenous and endogenous sources. We further introduce current knowledge on the possible roles of oxidative stress in skin pigmentation and aging, specifically with emphasis on oxidative stress and skin pigmentation. Meanwhile, we summarize the science and rationale of using three well-known antioxidants, namely vitamin C, resveratrol and ferulic acid, in the treatment of hyperpigmentation. Finally, we discuss the strategy for preventing oxidative stress-induced skin pigmentation and aging.

SIRT7 gene knockout using CRISPR/Cas9 system enhances melanin production in the melanoma cells

Melanin is a prominent pigment of skin and hair, and its deficiency can cause various disorders such as hair graying and albinism. The improvement of melanin production at a genetic level could offer an effective and permanent solution. Recently, SIRT7 has evoked an interest in the study of hair follicle stem cells, but its role in melanin synthesis remains unclear. In the present study, we have first successfully developed SIRT7 gene KO melanoma cells using the CRISPR/Cas9 system. It was found that the SIRT7 gene KO enhanced melanin production in melanoma cells. To validate the role of SIRT7 in melanin production, RT-PCR, western blot, and immunofluorescence staining assays were performed. The expression levels of melanin-producing genes and proteins (MITF, TRP1, TRP-2, TYR, TH) were significantly increased in SIRT7 gene KO cells compared to normal cells. In addition, melanin production was increased in KO cells higher than in normal cells through the image analysis. All these results suggest that SIRT7 could play an essential role in regulating melanin production, providing an alternative drug target to treat pigmentary disorders.

Natural and synthetic flavonoid derivatives as new potential tyrosinase inhibitors: a systematic review

Tyrosinase is a multifunctional glycosylated and copper-containing oxidase that is highly prevalent in plants and animals and plays a pivotal role in catalyzing the two key steps of melanogenesis: tyrosine's hydroxylation to dihydroxyphenylalanine (DOPA), and oxidation of the latter species to dopaquinone. Melanin guards against the destructive effects of ultraviolet radiation which is known to produce considerable pathological disorders such as skin cancer, among others. Moreover, the overproduction of melanin can create aesthetic problems along with serious disorders linked to hyperpigmented spots or patches on skin. Several skin-whitening products which reduce melanogenesis activity and alleviate hyperpigmentation are commercially available. A few of them, particularly those obtained from natural sources and that incorporate a phenolic scaffold, have been exploited in the cosmetic industry. In this context, synthetic tyrosinase inhibitors (TIs) with elevated efficacy and fewer side effects are direly needed in the pharmaceutical and cosmetic industries owing to their protective effect against pigmentation and dermatological disorders. Furthermore, the biological significance of the chromone skeleton and its associated medicinal and bioactive properties has drawn immense interest and inspired many researchers to design and develop novel anti-tyrosinase agents based on the flavonoid core (2-arylchromone). This review article is oriented to provide an insight and a deeper understanding of the tyrosinase inhibitory activity of an array of natural and bioinspired phenolic compounds with special emphasis on flavonoids to demonstrate how the position of ring substituents and their interaction with tyrosinase could be correlated with their effectiveness or lack thereof against inhibiting the enzyme.

Anti-Pigmentary Natural Compounds and Their Mode of Action

Hyper-activated melanocytes are the major cause of skin hyper-pigmentary disorders, such as freckles and melasma. Increasing efforts have been made to search for materials with depigmenting activity to develop functional cosmetics. As a result, numerous materials have been reported to have depigmenting activity but some of them are known to cause unwanted side effects. Consequently, anti-pigmentary natural compounds without concern of toxicity are in great demand. Virtually all sorts of natural sources have been investigated to find anti-pigmentary natural compounds. This review summarizes recently reported anti-pigmentary natural compounds and their mode of action from the ocean, plants, and bacteria.