Isoliquiritigenin inhibits melanogenesis, melanocyte dendricity and melanosome transport by regulating ERK-mediated MITF degradation

Components analysis of San-Bai decoction, and its pharmacodynamics and mechanism on preventing and treating melasma

ETHNOPHARMACOLOGICAL RELEVANCE

San-Bai Decoction (SBD) is a classic whitening prescription originally recorded in the 'Introduction to Medicine' of the Ming Dynasty. SBD has been known for invigorating Qi and blood, promoting spleen and stomach, whitening skin, and fading melasma. However, its pharmacodynamic material basis and specific mechanism remain unclear.

AIM OF THE STUDY

The aim of this study is to clarify the pharmacodynamic material basis of SBD and its mechanism of removing melasma.

MATERIALS AND METHODS

The positive and negative ion mass spectrum data of SBD extract were collected by UHPLC-Q-Exactive Orbitrap MS/MS, imported into Compound Discoverer (CD) 3.1 software, matched through the online database, and manually checked. Finally, the in vitro chemical components of SBD were classified. Similarly, the mass spectrum data of SBD in the serum of normal rats and melasma model rats were also analyzed by CD 3.1 software. The in vitro identified Compound file of SBD was imported into the Expected Compounds and the Generate Expected Compounds project was selected. The SBD compounds were then chosen under the Compound Section. All phase I and II reaction types related to SBD components were selected, and the metabolic platform of CD 3.1 software was utilized to process the results and obtain possible metabolites. The metabolites were scored and products with high scores were subsequently screened. According to literature comparison, the final metabolites of SBD in both normal rats and melasma model rats were determined and comprehensively analyzed. The Melasma model rats were constructed through intramuscular injection of progesterone and ultraviolet radiation B (UVB) irradiation. The preventing and treating effect of SBD on melasma were evaluated by regulating inflammation, epidermal collagen content, and oxidative stress. Additionally, the effect of SBD on the Phosphatidylinositol 3-kinase (PI3K)/Protein kinase B (Akt)/Glycogen synthase kinase 3β (GSK3β) pathway was investigated through Western blot (WB) to explore its underlying mechanism on whitening and removing melasma efficacy.

RESULTS

Ultimately, 94 components were identified in SBD, including 41 flavonoids, 27 organic acids, and 9 glycosides, 3 terpenoids, 2 amides, 2 aldehydes, 1 phenylpropanoid and 9 other compounds. In the blood of normal rat group, a total of 24 prototype components and 61 metabolites were identified. Similarly, there were19 prototype components and 44 metabolites identified from the blood of melasma model rats. Pharmacodynamic experiment results indicated that SBD effectively reduced the incidence of melasma, prevent the loss of epidermal collagen, and elevate the activity of superoxide dismutase and decrease the malondialdehyde content in both liver and skin. Interestingly, the WB results demonstrated that SBD effectively activated PI3K/Akt/GSK3β pathway, and down-regulated the expression of melanin-related proteins.

CONCLUSIONS

For the first time, the components of SBD extracts, and its prototype components and metabolites in the blood of normal rats and melasma model rats were successfully identified by high-resolution liquid chromatography-mass spectrometry with CD software. Additionally, the differences of in vivo components of SBD between normal rats and melasma model rats were analyzed. The preventive and therapeutic effect of SBD on melasma was verified in the melasma model rats induced by progesterone and UVB irradiation, and its mechanism was related to activating PI3K/Akt/GSK3β pathway and downregulating the expression of melanin-related proteins. These results provide an experimental foundation for further research on the pharmacodynamic substance basis and pharmacodynamic mechanism of SBD, as well as developing new anti-melasma formula with SBD.

UVB-induced TRPS1 regulates MITF transcription activity to promote skin pigmentation

Hyperpigmented dermatoses are characterized by increased skin pigmentation caused by genetic, environmental factors and inflammation, which lasts a long time and is difficult to treat. Ultraviolet (UV), especially ultraviolet B (UVB), is the primary external factor inducing skin pigmentation. However, the specific regulatory mechanisms are not fully understood. Through analysis of GEO datasets from four UV-exposed skin cell/tissue samples, we found that TRPS1 is the only gene differentially expressed in multiple datasets (GSE22083, GSE67098 and GSE70280) and highly positively correlated with the expression of key melanogenesis genes. Consistently, we observed that TRPS1 is highly expressed in sun-exposed skin tissues compared to non-exposed skin. Additionally, the expression of TRPS1 was also significantly upregulated after UVB irradiation in isolated skin tissues and melanocytes, while knockdown of TRPS1 expression inhibited the UVB-induced melanogenesis. Further research revealed that overexpression of TRPS1 increased melanin content and tyrosinase activity in MNT1 cells, as well as upregulated the expression levels of key melanogenesis genes (MITF, TYR, TYRP1, DCT). In contrast, inhibition of TRPS1 expression showed the opposite effect. Moreover, we found that TRPS1 can bind to the promoter region of MITF, inhibiting the expression of MITF can antagonize the melanogenesis induced by TRPS1. In conclusion, UVB-induced TRPS1 promotes melanogenesis by activating the transcriptional activity of MITF.

Tribuloside acts on the PDE/cAMP/PKA pathway to enhance melanogenesis, melanocyte dendricity and melanosome transport

ETHNOPHARMACOLOGICAL RELEVANCE

Tribuloside, a natural flavonoid extracted from Chinese medicine Tribulus terrestris L., has shown potent efficacy in treating various diseases. In China, the fruits of Tribulus terrestris L. have long been utilized for relieving headache, dizziness, itchiness, and vitiligo. Water-based extract derived from Tribulus terrestris L. can enhance melanogenesis in mouse hair follicle melanocytes by elevating the expression of α-melanocyte stimulating hormone (α-MSH) and melanocortin-1 recepter (MC-1R). Nevertheless, there is a lack of information regarding the impact of tribuloside on pigmentation in both laboratory settings and living organisms.

AIM OF THE STUDY

The present research aimed to examine the impact of tribuloside on pigmentation, and delve into the underlying mechanism.

MATERIALS AND METHODS

Following the administration of tribuloside in human epidermal melanocytes (HEMCs), we utilized microplate reader, Masson-Fontana ammoniacal silver stain, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) to measure melanin contents, dendrite lengths, melanosome counts; L-DOPA oxidation assay to indicate tyrosinase activity, Western blotting to evaluate the expression of melanogenic and associated phosphodiesterase (PDE)/cyclic adenosine monophosphate (cAMP)/cyclic-AMP dependent protein kinase A (PKA) pathway proteins. A PDE-Glo assay to verify the inhibitory effect of tribuloside on PDE was also conducted. Additionally, we examined the impact of tribuloside on the pigmentation in both zebrafish model and human skin samples.

RESULTS

Tribuloside had a notable impact on the production of melanin in melanocytes, zebrafish, and human skin samples. These functions might be attributed to the inhibitory effect of tribuloside on PDE, which could increase the intracellular level of cAMP to stimulate the phosphorylation of cAMP-response element binding (CREB). Once activated, it induced microphthalmia-associated transcription factor (MITF) expression and increased the expression of tyrosinase, Rab27a and cell division cycle protein 42 (Cdc42), ultimately facilitating melanogenesis, melanocyte dendricity, and melanin transport.

CONCLUSION

Tribuloside acts on the PDE/cAMP/PKA pathway to enhance melanogenesis, melanocyte dendricity, and melanosome transport; meanwhile, tribuloside does not have any toxic effects on cells and may be introduced into clinical prescriptions to promote pigmentation.

The inhibition of VDAC1 oligomerization promotes pigmentation through the CaMK-CRTCs/CREB-MITF pathway

The voltage-dependent anion channel 1 (VDAC1) forms an oligomeric structure on the mitochondrial outer membrane, which plays critical roles in many physiological processes. Research studies have demonstrated that the knockout of VDAC1 increases pigment content and up-regulates the expression of melanogenic genes. Due to its involvement in various physiological processes, the depletion of VDAC1 has significant detrimental effects on cellular functions and the inhibition of VDAC1 oligomerization has recently emerged as a promising strategy for the treatment of several diseases. In this study, we found that VDAC1 oligomerization inhibitors, VBIT-12 and NSC-15364, promote melanogenesis, dendrite formation and melanosome transport in human epidermal melanocytes (HEMCs). Mechanistically, treatment of HEMCs with an oligomerization inhibitor increased the level of cytoplasmic calcium ions, which activated calcium-calmodulin dependent protein kinase (CaMK) and led to the phosphorylation of CREB and the nuclear translocation of CREB-regulated transcription coactivators (CRTCs). Subsequently, CRTCs, p-CREB and CREB-binding protein (CBP) in the nucleus cooperatively recruit the transcription machinery to initiate the transcription of MITF thus promoting pigmentation. Importantly, our study also demonstrates that VDAC1 oligomerization inhibitors increase pigmentation in zebrafish and in human skin explants, highlighting their potential as a therapeutic strategy for skin pigmentation disorders.

Fraxin inhibits melanogenesis by suppressing the ERK/MAPK pathway and antagonizes oxidative stress by activating the NRF2 pathway

Hyperpigmentation disorders, such as melasma and freckles, are highly prevalent and draw increasing attention. Patients thus tend to seek effective and safe cosmetic whitening agents. Fraxin, a bioactive substance extracted from Cortex Fraxini, possesses anti-inflammation and antioxidant properties. In this study, we further explored the anti-melanogenic activities of fraxin were explored in vitro and in vivo. We found that pretreatment with fraxin decreased the melanin content of MNT1 cells and zebrafishes. In MNT1 cells, melanogenesis-related proteins, such as MITF, TYR, TYRP1, and DCT were down-regulated and tyrosinase activity was reduced under fraxin treatment. Further exploration of the mechanism revealed that fraxin could inhibit the phosphorylation of ERK, which is closely related to melanogenesis. Besides, fraxin also protected MNT1 cells from H2O2-induced apoptosis via scavenging reactive oxygen species (ROS) in cells. Further experimentation revealed that fraxin could activate NRF2 and upregulate antioxidase CAT and HO-1. In conclusion, fraxin could be an effective agent with anti-melanogenesis and antioxidant properties for hyperpigmentation disorders.

Optimization of Monobenzone-Induced Vitiligo Mouse Model by the Addition of Chronic Stress

Vitiligo is a common primary, limited or generalized skin depigmentation disorder. Its pathogenesis is complex, multifactorial and unclear. For this reason, few animal models can simulate the onset of vitiligo, and studies of drug interventions are limited. Studies have found that there may be a pathophysiological connection between mental factors and the development of vitiligo. At present, the construction methods of the vitiligo model mainly include chemical induction and autoimmune induction against melanocytes. Mental factors are not taken into account in existing models. Therefore, in this study, mental inducement was added to the monobenzone (MBEH)-induced vitiligo model. We determined that chronic unpredictable mild stress (CUMS) inhibited the melanogenesis of skin. MBEH inhibited melanin production without affecting the behavioral state of mice, but mice in the MBEH combined with CUMS (MC) group were depressed and demonstrated increased depigmentation of the skin. Further analysis of metabolic differences showed that all three models altered the metabolic profile of the skin. In summary, we successfully constructed a vitiligo mouse model induced by MBEH combined with CUMS, which may be better used in the evaluation and study of vitiligo drugs.

Quercetin 3-O-(6″-O-E-caffeoyl)-β-D-glucopyranoside, a Flavonoid Compound, Promotes Melanogenesis through the Upregulation of MAPKs and Akt/GSK3β/β-Catenin Signaling Pathways

Quercetin 3-O-(6″-O-E-caffeoyl)-β-D-glucopyranoside is a flavonoid compound produced by various plants with reported antiprotozoal potential against E. histolytica and G. lamblia; however, its effects on skin pigment regulation have not been studied in detail. In this investigation, we discovered that quercetin 3-O-(6″-O-E-caffeoyl)-D-glucopyranoside (coded as CC7) demonstrated a more increased melanogenesis effect in B16 cells. CC7 exhibited no cytotoxicity or effective stimulating melanin content or intracellular tyrosinase activity. This melanogenic-promoting effect was accompanied by activated expression levels of microphthalmia-associated transcription factor (MITF), a key melanogenic regulatory factor, melanogenic enzymes, and tyrosinase (TYR) and tyrosinase-related protein-1 (TRP-1) and 2 (TRP-2) in the CC7-treated cells. Mechanistically, we found that CC7 exerted melanogenic effects by upregulating the phosphorylation of stress-regulated protein kinase (p38) and c-Jun N-terminal kinase (JNK). Moreover, the CC7 upregulation of phosphor-protein kinase B (Akt) and Glycogen synthase kinase-3 beta (GSK-3β) increased the content of β-catenin in the cell cytoplasm, and subsequently, it translocated into the nucleus, resulting in melanogenesis. Specific inhibitors of P38, JNK, and Akt validated that CC7 promotes melanin synthesis and tyrosinase activity by regulating the GSK3β/β-catenin signaling pathways. Our results support that the CC7 regulation of melanogenesis involves MAPKs and Akt/GSK3β/β-catenin signaling pathways.

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.

Natural products in cosmetics

The global cosmetics market reached US$500 billion in 2017 and is expected to exceed US$800 billion by 2023, at around a 7% annual growth rate. The cosmetics industry is emerging as one of the fastest-growing industries of the past decade. Data shows that the Chinese cosmetics market was US$60 billion in 2021. It is expected to be the world's number one consumer cosmetics market by 2050, with a size of approximately US$450 billion. The influence of social media and the internet has raised awareness of the risks associated with the usage of many chemicals in cosmetics and the health benefits of natural products derived from plants and other natural resources. As a result, the cosmetic industry is now paying more attention to natural products. The present review focus on the possible applications of natural products from various biological sources in skin care cosmetics, including topical care products, fragrances, moisturizers, UV protective, and anti-wrinkle products. In addition, the mechanisms of targets for evaluation of active ingredients in cosmetics and the possible benefits of these bioactive compounds in rejuvenation and health, and their potential role in cosmetics are also discussed.

Pterostilbene inhibits melanogenesis, melanocyte dendricity and melanosome transport through cAMP/PKA/CREB pathway

Pterostilbene is a trans stilbene compound, which is an effective component of herbaceous plants such as Dalbergia woods and Vaccinium. Although pterostilbene has many uses in anti-inflammatory, anti-oxidant and anti-tumor, its whitening effect is drawing more and more attention, the mechanism of melanogenesis and melanosome transport still needs further study. In this research, we tried to further investigate how melanocyte melanogenesis is affected by pterostilbene and whether pterostilbene play a part in melanin transport. Our results showed that pterostilbene has a potent inhibitory effect on melanogenesis in B16F10 cells (3 μM, p < 0.001), in-vitro human skin (10 μM, p < 0.05) and zebrafish embryos (3 μM, p < 0.01). Besides, pterostilbene not only inhibited melanogenesis, but also inhibited melanocyte dendritic development and melanosome transport. Pterostilbene mainly plays a role by inhibiting cAMP/PKA/CREB signal pathway. After the cAMP/PKA/CREB signaling pathway was inhibited, tyrosinase activity and the expression of MITF, TYR, Rab27A, Rab17 and gp100 were decreased, which in turn suppressed melanogenesis, melanocyte dendritic development and melanosome transport. Our findings showed that pterostilbene can potently inhibit melanogenesis and melanosome transport, suggesting the applicability of pterostilbene in skin lightning. Therefore, a novel pharmacologic way to treat hyperpigmentation has been proposed.

Spectrum-effect relationship between HPLC fingerprint and antioxidant of "San-Bai Decoction" extracts

"San-Bai Decoction" (SBD) has been a traditional Chinese medicine compound preparation for replenishing Qi and promoting blood circulation, whitening skin, and removing blemishes since ancient times. However, its chemical composition and antioxidant activity are not clear thus far, which limits the in-depth study on its pharmacodynamic material basis and efficacy. The objective of this study was to establish the fingerprint profile of SBD, assess its antioxidant activity by measuring 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability, and find the spectrum-effect relationship of SBD by Grey Relation Analysis (GRA) and Partial Least Squares Regression (PLS). In this study, the fingerprint of SBD was established by high performance liquid chromatography (HPLC), and 20 common peaks were found, among which 6 peaks were designated. The similarities between the fingerprints of 12 batches of SBD and the reference fingerprint (R) were all greater than 0.900. Meanwhile, the antioxidant activities of all batches were concentration-dependent in their linear regression equation. The result of GRA showed that the correlation order of 20 common peaks for DPPH radical scavenging was X13 > X7 > X3 > X6 > X10 > X11 > X4 > X12 > X2 > X18 > X9 > X5 > X19 > X1 > X20 > X16 > X17 > X15 > X8 > X14. At the same time, PLS study demonstrated that the contribution of six identified characteristic peaks to DPPH radical scavenging ability was X1 = X7 > X6 > X19 > X20 > X16. In this study, the spectrum-effect relationship of SBD between its HPLC fingerprint and the antioxidant activity can be used to screen the pharmacodynamic substance basis of its antioxidant action and lay the foundation for establishing quality standards and product development.

Role of Phytochemicals in Skin Photoprotection via Regulation of Nrf2

Ethnopharmacological studies have become increasingly valuable in the development of botanical products and their bioactive phytochemicals as novel and effective preventive and therapeutic strategies for various diseases including skin photoaging and photodamage-related skin problems including abnormal pigmentation and inflammation. Exploring the roles of phytochemicals in mitigating ultraviolet radiation (UVR)-induced skin damage is thus of importance to offer insights into medicinal and ethnopharmacological potential for development of novel and effective photoprotective agents. UVR plays a role in the skin premature aging (or photoaging) or impaired skin integrity and function through triggering various biological responses of skin cells including apoptosis, oxidative stress, DNA damage and inflammation. In addition, melanin produced by epidermal melanocytes play a protective role against UVR-induced skin damage and therefore hyperpigmentation mediated by UV irradiation could reflect a sign of defensive response of the skin to stress. However, alteration in melanin synthesis may be implicated in skin damage, particularly in individuals with fair skin. Oxidative stress induced by UVR contributes to the process of skin aging and inflammation through the activation of related signaling pathways such as the mitogen-activated protein kinase (MAPK)/activator protein-1 (AP-1), the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt), the nuclear factor kappa B (NF-κB) and the signal transducer and activator of transcription (STAT) in epidermal keratinocytes and dermal fibroblasts. ROS formation induced by UVR also plays a role in regulation of melanogenesis in melanocytes via modulating MAPK, PI3K/Akt and the melanocortin 1 receptor (MC1R)-microphthalmia-associated transcription factor (MITF) signaling cascades. Additionally, nuclear factor erythroid 2-related factor 2 (Nrf2)-regulated antioxidant defenses can affect the major signaling pathways involved in regulation of photoaging, inflammation associated with skin barrier dysfunction and melanogenesis. This review thus highlights the roles of phytochemicals potentially acting as Nrf2 inducers in improving photoaging, inflammation and hyperpigmentation via regulation of cellular homeostasis involved in skin integrity and function. Taken together, understanding the role of phytochemicals targeting Nrf2 in photoprotection could provide an insight into potential development of natural products as a promising strategy to delay skin photoaging and improve skin conditions.

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.

Isoliquiritigenin Alleviates Semen Strychni-Induced Neurotoxicity by Restoring the Metabolic Pathway of Neurotransmitters in Rats

Acute neurotoxicity of Semen Strychni can result in sudden death in epilepsy. The detoxification method and mechanism of Semen Strychni acute poisoning have not been clarified. This experiment focused on the mechanism of Semen Strychni neurotoxicity and the alleviation effects of isoliquiritigenin. The rats were intraperitoneally injected with Semen Strychni extract (125 mg/kg), followed by oral administration of isoliquiritigenin (50 mg/kg) for 7 days. FJ-B staining was used to evaluate the degree of injury on hippocampus neurons. The concentration of monoamines, amino acids, and choline neurotransmitters, the Dopamine (DA) and 5-hydroxytryptamine (5-HT) metabolic pathway in the hippocampus, cerebellum, striatum, prefrontal cortex, hypothalamus, serum, and plasma were detected by LC-MS/MS. The expression of neurotransmitter metabolic enzymes [catechol-O-methyl transferase (COMT) and monoamine oxidase (MAO)] and neurotransmitter receptors [glutamate N-methyl-D-aspartic acid receptors (NMDARs) and gamma-aminobutyric acid type A receptor (GABRs)] were, respectively determined using ELISA and qRT-PCR. The results indicated that Semen Strychni induced neuronal degeneration in the hippocampal CA1 region. Meanwhile, Semen Strychni inhibited the mRNA expression of NMDAR1, NMDAR2A, NMDAR2B, GABRa1, GABRb2 and reduced the level of MAO, which disrupted the DA and 5-HT metabolic pathway. However, isoliquiritigenin reversed these effects. In summary, isoliquiritigenin showed alleviation effects on Semen Strychni-induced neurotoxicity, which could be attributed to restoring neurotransmitters metabolic pathway, most likely through the activation of NMDA receptors.

Salicylic acid in ginseng root alleviates skin hyperpigmentation disorders by inhibiting melanogenesis and melanosome transport

Abnormal melanogenesis and melanosome transport can cause skin pigmentation disorders that are often treated using ginseng-based formulation. We previously found that phenolic acid compounds in ginseng root could inhibit melanin production and as a skin-whitening agents. However, mechanisms of action underlying effects of ginseng phenolic acid monomers on melanogenesis remain unclear. This study was conducted to investigate effects of salicylic acid, a main ginseng root phenolic acid component, on melanogenesis and melanosome functions in melanocytes of zebrafish and other species. Salicylic acid exhibited no cytotoxicity and reduced melanin levels and tyrosinase activity in B16F10 murine melanoma cells and normal human epidermal melanocytes regardless of prior cell stimulation with α-melanocyte stimulating hormone. Additionally, salicylic acid treatment reduced expression of melanogenic enzymes tyrosinase, tyrosinase-related protein 1 and tyrosinase-related protein 2, while reducing expression of their master transcriptional regulator, microphthalmia-associated transcription factor. Moreover, reduced phosphorylation of cAMP response-element binding protein was observed due to reduced cAMP levels resulting from salicylic acid inhibition of upstream signal regulators (adenylyl cyclase and protein kinase A). Furthermore, salicylic acid treatment suppressed expression of transport complex-associated proteins melanophilin and myosin Va in two UVB-treated melanocytic cell lines, suppressed phagocytosis of fluorescent microspheres by UVB-stimulated human keratinocytes (HaCaT), inhibited protease-activated receptor 2 activation by reducing both Ca²⁺ release and activation of phosphoinositide 3 kinase/AKT and mitogen-activated protein kinases and induced anti-melanogenic effects in zebrafish. Collectively, these results indicate that salicylic acid within ginseng root can inhibit melanocyte melanogenesis and melanin transport, while also suppressing keratinocyte phagocytic function.

Cajanin Suppresses Melanin Synthesis through Modulating MITF in Human Melanin-Producing Cells

Despite its classification as a non-life-threatening disease, increased skin pigmentation adversely affects quality of life and leads to loss of self-confidence. Until now, there are no recommended remedies with high efficacy and human safety for hyperpigmentation. This study aimed to investigate anti-melanogenic activity and underlying mechanism of cajanin, an isoflavonoid extracted from Dalbergia parviflora Roxb. (Leguminosae) in human melanin-producing cells. Culture with 50 μM cajanin for 48–72 h significantly suppressed proliferation in human melanoma MNT1 cells assessed via MTT viability assay. Interestingly, cajanin also efficiently diminished melanin content in MNT1 cells with the half maximum inhibitory concentration (IC₅₀) at 77.47 ± 9.28 μM. Instead of direct inactivating enzymatic function of human tyrosinase, down-regulated mRNA and protein expression levels of MITF and downstream melanogenic enzymes, including tyrosinase, TRP-1 and Dct (TRP-2) were observed in MNT1 cells treated with 50 μM cajanin for 24–72 h. Correspondingly, treatment with cajanin modulated the signaling pathway of CREB and ERK which both regulate MITF expression level. Targeted suppression on MITF-related proteins in human melanin-producing cells strengthens the potential development of cajanin as an effective treatment for human hyperpigmented disorders.

Antioxidant and Anti-Melanogenic Activities of Heat-Treated Licorice (Wongam, Glycyrrhiza glabra × G. uralensis) Extract

Melanin is a brown or black pigment that protects skin from ultraviolet radiation and reactive oxygen species (ROS). However, overproduction of melanin is associated with lentigines, melasma, freckles and skin cancer. Licorice has shown antioxidant, anti-tumor, anti-platelet, anti-inflammatory and immunomodulatory activities and is used as a natural treatment for skin whitening. We aimed to confirm the potential of Wongam, a new cultivar of licorice developed by the Rural Development Administration (RDA), as a whitening agent in cosmetics. In addition, we verified the effect of heat treatment on the bioactivity of licorice by comparing antioxidant and anti-melanogenic activities of licorice extract before and after heating (130 °C). The heat-treated licorice extract (WH-130) showed higher radical-scavenging activities in the ABTS⁺ (2,2′-azino-bis-(3-ethylbenzothiazolin-6-sulfonic acid) diammonium salt) and DPPH (2,2-diphenyl-1-picrylhydrazyl) assays. In addition, WH-130 inhibited melanogenesis more effectively due to downregulation of tyrosinase in B16F10 melanoma cells than non-heated licorice extract. Moreover, heat treatment increased total phenolic content. In particular, isoliquiritigenin, an antioxidant and anti-melanogenic compound of licorice, was produced by heat treatment. In conclusion, WH-130, with increased levels of bioactive phenolics such as isoliquiritigenin, has potential for development into a novel skin whitening material with applications in cosmetics.

UDP-GlcNAc-1-Phosphotransferase Is a Clinically Important Regulator of Human and Mouse Hair Pigmentation

UDP-GlcNAc-1-phosphotransferase, a product of two separate genes (GNPTAB, GNPTG), is essential for the sorting and transportation of lysosomal enzymes to lysosomes. GNPTAB gene defects cause extracellular missorting of lysosomal enzymes resulting in lysosomal storage diseases, namely mucolipidosis type II and mucolipidosis type III alpha/beta, which is associated with hair discoloration. Yet, the physiological functions of GNPTAB in the control of hair follicle (HF) pigmentation remain unknown. To elucidate these, we have silenced GNPTAB in organ-cultured human HFs as a human ex vivo model for mucolipidosis type II. GNPTAB silencing profoundly inhibited intrafollicular melanin production, the correct sorting of melanosomes, tyrosinase activity, and HMB45 expression in the HF pigmentary unit and altered HF melanocyte morphology in situ. In isolated primary human HF melanocytes, GNPTAB knockdown significantly reduced melanogenesis, tyrosinase activity, and correct tyrosinase protein sorting as well as POMC expression and caused the expected lysosomal enzyme missorting in vitro. Moreover, transgenic mice overexpressing an inserted missense mutation corresponding to that seen in human mucolipidosis type II and mucolipidosis type III alpha/beta showed significantly reduced HF pigmentation, thus corroborating the in vivo relevance of our ex vivo and in vitro findings in the human system. This identifies GNPTAB as a clinically important enzymatic control of human HF pigmentation, likely by directly controlling tyrosinase sorting and POMC transcription in HF melanocytes.

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.

Perspectives on the Role of Isoliquiritigenin in Cancer

Isoliquiritigenin (2',4',4-trihydroxychalcone, ISL), one of the most important bioactive compounds with a chalcone structure, is derived from licorice root. Licorice is commonly known as Glycyrrhiza, including Glycyrrhiza uralensis, Glycyrrhiza radix, and Glycyrrhiza glabra, which are generally available in common foods and Chinese herbal medicines based on a wide variety of biological functions and pharmacological effects, and its derivative (ISL) is utilized as a food additive and adjunct disease treatment. In this review, we summarized the progress over the last 10 years in the targeted pathways and molecular mechanisms of ISL that are involved in the regulation of the onset and progression of different types of cancers.

FGIN-1-27 Inhibits Melanogenesis by Regulating Protein Kinase A/cAMP-Responsive Element-Binding, Protein Kinase C-β, and Mitogen-Activated Protein Kinase Pathways

FGIN-1-27 is a synthetic mitochondrial diazepam binding inhibitor receptor (MDR) agonist that has demonstrated pro-apoptotic, anti-anxiety, and steroidogenic activity in various studies. Here we report, for the first time, the anti-melanogenic efficacy of FGIN-1-27 in vitro and in vivo. FGIN-1-27 significantly inhibited basal and α-melanocyte-stimulating hormone (α-MSH)-, 1-Oleoyl-2-acetyl-sn-glycerol (OAG)- and Endothelin-1 (ET-1)-induced melanogenesis without cellular toxicity. Mushroom tyrosinase activity assay showed that FGIN-1-27 did not directly inhibit tyrosinase activity, which suggested that FGIN-1-27 was not a direct inhibitor of tyrosinase. Although it was not capable of modulating the catalytic activity of mushroom tyrosinase in vitro, FGIN-1-27 downregulated the expression levels of key proteins that function in melanogenesis. FGIN-1-27 played these functions mainly by suppressing the PKA/CREB, PKC-β, and MAPK pathways. Once inactivated, it decreased the expression of MITF, tyrosinase, TRP-1, TRP-2, and inhibited the tyrosinase activity, finally inhibiting melanogenesis. During in vivo experiments, FGIN-1-27 inhibited the body pigmentation of zebrafish and reduced UVB-induced hyperpigmentation in guinea pig skin, but not a reduction of numbers of melanocytes. Our findings indicated that FGIN-1-27 exhibited no cytotoxicity and inhibited melanogenesis in both in vitro and in vivo models. It may prove quite useful as a safer skin-whitening agent.

Beta amyloid-induced time-dependent learning and memory impairment: involvement of HPA axis dysfunction

Aβ aggregation is one of the pathological biomarkers of Alzheimer's disease (AD). However, the possible mechanism related to Aβ-induced pathological signaling pathway is still unknown. In the present study, Aβ1-42-induced time-dependent memory impairment and its possible relationship to hypothalamic-pituitary-adrenal (HPA) axis hyperactivity were examined. Aβ1-42-treated mice significantly impaired acquisition activity in the learning curve at 10 days, 1 and 4 months in the Morris water-maze (MWM) task. This learning activity was back to normal at 8 months after Aβ1-42 treatment. In the probe trial test, Aβ1-42-treated mice needed longer latencies to touch the precious platform location and fewer numbers of crossing from 10 days to 4 months after microinjection. This Aβ1-42 induced memory loss was consistent with the results of the step-down passive avoidance test. The HPA axis related parameters, such as corticosterone (CORT) level in the serum, glucocorticoid receptor (GR) and corticotropin-releasing factor receptor (CRF-R) expression in the frontal cortex and hippocampus increased in Aβ1-42-treated mice from 10 days to 4 months. While the downstream molecules phosphorylation of cyclic AMP response element binding (pCREB) and brain-derived neurotrophic factor (BDNF) expression decreased during this time. These effects were back to normal 8 months after treatment with Aβ1-42. Altogether, our results suggested that Aβ1-42 induced significant learning and memory impairment, which is involved in HPA axis dysfunction.

CMT-308, a Nonantimicrobial Chemically-Modified Tetracycline, Exhibits Anti-Melanogenic Activity by Suppression of Melanosome Export

CMT-308 is a nonantimicrobial chemically-modified tetracycline (CMT), which we have previously shown exhibits antifungal activity and pleiotropic anti-inflammatory activities, including inhibition of the enzymatic activity of matrix metalloproteinases (MMPs). Based on its chemical structure, we hypothesized that CMT-308 could inhibit melanogenesis and might be a candidate for the treatment of skin hyperpigmentation disorders which occur due to unregulated melanin biosynthesis and/or transport. CMT-308 was first studied for any effects on activity of the enzyme tyrosinase in vitro using a purified preparation of mushroom tyrosinase; the mode of inhibition of the soluble fungal enzyme was evaluated by Lineweaver-Burk and Dixon plots as well as by non-linear least squares fitting. Next, the effects of CMT-308 were tested in mammalian cell cultures using B16F10 mouse melanoma cells and further validated in darkly-pigmented human melanocytes (HEMn-DP). Our results showed that micromolar concentrations of CMT-308 inhibited mushroom tyrosinase enzyme activity, using the first two substrates in the melanogenesis pathway (l-tyrosine and l-3,4-dihydroxyphenylalanine (l-DOPA)); CMT-308 inhibited mushroom tyrosinase primarily via a mixed mode of inhibition, with the major contribution from a competitive mode. In B16F10 cell cultures, CMT-308 (10 µM) significantly diminished total melanin levels with a selective reduction of extracellular melanin levels, under both basal and hormone-stimulated conditions without any cytotoxicity over a duration of 72 h. Studies of potential mechanisms of inhibition of melanogenesis in B16F10 cells showed that, in mammalian cells, CMT-308 did not inhibit intracellular tyrosinase activity or the activity of α-glucosidase, an enzyme that regulates maturation of tyrosinase. However, CMT-308 suppressed MITF protein expression in B16F10 cells and showed copper chelating activity and antioxidant activity in a cell-free system. The significantly lower extracellular melanin levels obtained at 10 µM indicate that CMT-308’s anti-melanogenic action may be attributed to a selective inhibition of melanosome export with the perinuclear aggregation of melanosomes, rather than a direct effect on the tyrosinase-catalyzed steps in melanin biosynthesis. These results were validated in HEMn-DP cells where CMT-308 suppressed dendricity in a fully reversible manner without affecting intracellular melanin synthesis. Furthermore, the capacity of CMT-308 to inhibit melanosome export was retained in cocultures of HEMn-DP and HaCaT. In summary, our results offer promise for therapeutic strategies to combat the effects of hyperpigmentation by use of CMT-308 at low micromolar concentrations.

Protoporphyrin IX Stimulates Melanogenesis, Melanocyte Dendricity, and Melanosome Transport Through the cGMP/PKG Pathway

Protoporphyrin IX (PPIX) is a heterocyclic organic compound that is the last intermediate in the heme biosynthetic pathway. PPIX, due to its photodynamic effects, is utilized in the treatment of skin diseases. Furthermore, PPIX has been utilized as a melanogenesis-stimulating agent in various studies. However, the exact function and mechanism underlying PPIX action in melanocytes remain to be elucidated. In the present study, we sought to further investigate how PPIX affects melanocyte melanogenesis, and whether PPIX is involved in melanin transport. Our findings demonstrated that PPIX increased melanocyte dendricity and melanosome transport, in addition to increasing melanogenesis. PPIX functions primarily by activating the guanylate cyclase (GC) and cyclic guanosine 3’, 5’-monophosphate/protein kinase G (cGMP/PKG) signaling pathways. Once activated, these pathways increase tyrosinase activity and the expression of microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein-1 and -2 (TRP-1 and TRP-2), myosin Va, melanophinin, Ras-related protein Rab-27A (Rab27a), and cell division cycle 42 (Cdc42), promoting melanogenesis, melanocyte dendricity, and melanosome transport. Furthermore, the melanogenic effects of PPIX were confirmed in vivo in a zebrafish model system. Our results indicate that PPIX is not cytotoxic and may, thus, be utilized as a pigmentation enhancer.

Inhibitory Effects of the Bioactive Thermorubin Isolated from the Fungus Thermoactinomyces Antibioticus on Melanogenesis

Skin hyperpigmentation disorders arise due to aberrant regulation of melanin synthesis and export. Current treatments include natural compounds like kojic acid and hydroquinone, which suffer from limitations due to adverse reactions. Thermorubin (TR) is a secondary metabolite derived from the fungus Thermoactinomyces antibioticus and has previously demonstrated to possess anti-inflammatory properties by inhibition of matrix metalloproteinases (MMPs), as well as antimicrobial activity. In the current study, we explored whether TR might be a used as a candidate for the treatment of skin hyperpigmentation disorders by studying its effects on melanin synthesis and melanin export in B16F10 mouse melanoma cells and primary human melanocytes derived from darkly-pigmented (DP) skin. Non-toxic doses of TR were first identified in B16F10 mouse melanoma cells. These doses were subsequently tested for their effects on both extracellular and intracellular melanin levels under conditions of basal and hormone-stimulated melanogenesis. Our results demonstrated that TR at 25 µM inhibited total melanin levels with selective inhibition of extracellular melanin in B16F10 cells under both basal and hormone-stimulated conditions. The mechanisms of inhibition did not include tyrosinase inhibition, either in cellular lysates or cell-free system. However, TR potently inhibited activity of α-glucosidase enzyme in vitro and exhibited antioxidant activity. Furthermore, our results with primary human melanocytes from DP skin showed that TR at 10 µM significantly suppressed dendricity along with an increase in accumulation of intracellular melanin. These findings point to a mechanism of action of TR as an exclusive inhibitor of melanosome export. Taken together, our preliminary results demonstrate that TR might offer a novel ingredient as a skin depigmenting agent for inclusion in cosmetic formulations. Further studies delineating molecular mechanisms of hypopigmentation of TR and testing in human skin tissue-equivalents are warranted.

Sub-Acute Treatment of Curcumin Derivative J147 Ameliorates Depression-Like Behavior Through 5-HT1A-Mediated cAMP Signaling

Background

Major depressive disorder (MDD) is a severe mental disorder related to the deficiency of monoamine neurotransmitters, particularly to abnormalities of 5-HT (5-hydroxytryptamine, serotonin) and its receptors. Our previous study suggested that acute treatment with a novel curcumin derivative J147 exhibited antidepressant-like effects by increasing brain derived neurotrophic factor (BDNF) level in the hippocampus of mice. The present study expanded upon our previous findings and investigated the antidepressant-like effects of sub-acute treatment of J147 for 3 days in male ICR mice and its possible relevancy to 5-HT_1A and 5-HT_1B receptors and downstream cAMP-BDNF signaling.

Methods

J147 at doses of 1, 3, and 9 mg/kg (via gavage) was administered for 3 days, and the anti-immobility time in the forced swimming and tail suspension tests (FST and TST) was recorded. The radioligand binding assay was used to determine the affinity of J147 to 5-HT_1A and 5-HT_1B receptor. Moreover, 5-HT_1A or 5-HT_1B agonist or its antagonist was used to determine which 5-HT receptor subtype is involved in the antidepressant-like effects of J147. The downstream signaling molecules such as cAMP, PKA, pCREB, and BDNF were also measured to determine the mechanism of action.

Results

The results demonstrated that sub-acute treatment of J147 remarkably decreased the immobility time in both the FST and TST in a dose-dependent manner. J147 displayed high affinity in vitro to 5-HT_1A receptor prepared from mice cortical tissue and was less potent at 5-HT_1B receptor. These effects of J147 were blocked by pretreatment with a 5-HT_1A antagonist NAD-299 and enhanced by a 5-HT_1A agonist 8-OH-DPAT. However, 5-HT_1B receptor antagonist NAS-181 did not appreciably alter the effects of J147 on depression-like behaviors. Moreover, pretreatment with NAD-299 blocked J147-induced increases in cAMP, PKA, pCREB, and BDNF expression in the hippocampus, while 8-OH-DPAT enhanced the effects of J147 on these proteins’ expression.

Conclusion

The results suggest that J147 induces rapid antidepressant-like effects during a 3-day treatment period without inducing drug tolerance. These effects might be mediated by 5-HT_1A-dependent cAMP/PKA/pCREB/BDNF signaling.

Natural Chalcones in Chinese Materia Medica: Licorice

Licorice is an important Chinese materia medica frequently used in clinical practice, which contains more than 20 triterpenoids and 300 flavonoids. Chalcone, one of the major classes of flavonoid, has a variety of biological activities and is widely distributed in nature. To date, about 42 chalcones have been isolated and identified from licorice. These chalcones play a pivotal role when licorice exerts its pharmacological effects. According to the research reports, these compounds have a wide range of biological activities, containing anticancer, anti-inflammatory, antimicrobial, antioxidative, antiviral, antidiabetic, antidepressive, hepatoprotective activities, and so on. This review aims to summarize structures and biological activities of chalcones from licorice. We hope that this work can provide a theoretical basis for the further studies of chalcones from licorice.