Involvement of adenylate cyclase/cAMP/CREB and SOX9/MITF in melanogenesis to prevent vitiligo

Targeting Periplakin of Novel Benzenesulfonamides as Highly Selective Agonists for the Treatment of Vitiligo

Vitiligo is the most common cause of depigmentation worldwide, with immunosuppressive treatments often being inefficient and prone to recurrence, making it essential to identify new therapeutic targets. Periplakin (PPL) has been identified and confirmed as a key factor in vitiligo-related depigmentation. Based on this, a series of selective PPL agonists, specifically benzenesulfonamides, have been developed. Among these, compound I-3 exhibits superior efficacy compared to ruxolitinib, the only FDA-approved treatment for vitiligo. I-3 has been shown to increase cAMP levels by regulating PPL, which enhances MITF expression, a key transcription factor in melanin biosynthesis. Additionally, I-3 promotes melanin production by regulating tryptophan metabolism. In summary, PPL is a promising drug target, and I-3 has strong potential for future treatment of vitiligo due to its high selectivity and favorable druggability.

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.

Identification of candidate genes associated with primary feathers of tianfu nonghua ducks based on Genome-wide association studies

The primary feathers of ducks have important economic value in the poultry industry. This study quantified the primary feather phenotype of Nonghua ducks, including the primary feathers' length, area, distribution of black spots, and feather symmetry. And genome-wide association analysis was used to screen candidate genes that affect the primary feather traits. The genome-wide association study (GWAS) results identified the genetic region related to feather length (FL) on chromosome 2. Through Linkage disequilibrium (LD) analysis, candidate regions (chr2: 115,246,393-116,501,448 bp) were identified and were further annotated to 5 genes: MRS2, GPLD1, ALDH5A1, KIAA0319, and ATP9B. Secondly, candidate regions related to feather black spots were identified on chromosome 21. Through LD analysis, the candidate regions (chr21: 163,552-2,183,853 bp) were screened and further annotated to 47 genes. Among them, STK4, CCN5, and YWHAB genes were related to melanin-related pathways or pigment deposition, which may be key genes affecting the distribution of black spots on feathers. In addition, we also screened 125 genes on multiple chromosomes that may be related to feather symmetry. Among them, significant SNPs on chromosome 1 were further identified as candidate regions (chr1: 142,118,209-142,223,605 bp) through LD analysis and annotated into 2 genes, TGFBRAP1 and LOC113839965. These results reported the genetic basis of the primary feather from multiple phenotypes, and offered valuable insights into the genetic basis for the growth and development of duck feathers and feather color pattern.

Molecular characterization of transcription factor CREB3L2 and CREB3L3 and their role in melanogenesis in Pacific oysters (Crassostrea gigas)

Colorful shells in mollusks are commonly attributable to the presence of biological pigments. In Pacific oysters, the inheritance patterns of several shell colors have been investigated, but little is known about the molecular mechanisms of melanogenesis and pigmentation. cAMP-response element binding proteins (CREB) are important transcription factors in the cAMP-mediated melanogenesis pathway. In this study, we characterized two CREB genes (CREB3L2 and CREB3L3) from Pacific oysters. Both of them contained a conserved DNA-binding and dimerization domain (a basic-leucine zipper domain). CREB3L2 and CREB3L3 were expressed highly in the mantle tissues and exhibited higher expression levels in the black-shell oyster than in the white. Masson-Fontana melanin staining and immunofluorescence analysis showed that the location of CREB3L2 protein was generally consistent with the distribution of melanin in oyster edge mantle. Dual-luciferase reporter assays revealed that CREB3L2 and CREB3L3 could activate the microphthalmia-associated transcription factor (MITF) promoter and this process was regulated by the level of cAMP. Additionally, we found that cAMP regulated melanogenic gene expression through the CREB-MITF-TYR axis. These results implied that CREB3L2 and CREB3L3 play important roles in melanin synthesis and pigmentation in Pacific oysters.

cAMP-Mediated CREM-MITF-TYR Axis Regulates Melanin Synthesis in Pacific Oysters

Colorful shells in bivalves are mostly caused by the presence of biological pigments, among which melanin is a key component in the formation of shell colours. Cyclic adenosine monophosphate (cAMP) is an important messenger in the regulation of pigmentation in some species. However, the role of cAMP in bivalve melanogenesis has not yet been reported. In this study, we performed in vitro and in vivo experiments to determine the role of cAMP in regulating melanogenesis in Pacific oysters. Besides, the function of cAMP-responsive element modulator (CREM) and the interactions between CREM and melanogenic genes were investigated. Our results showed that a high level of cAMP promotes the expression of melanogenic genes in Pacific oysters. CREM controls the expression of the MITF gene under cAMP regulation. In addition, CREM can regulate melanogenic gene expression, tyrosine metabolism, and melanin synthesis. These results indicate that cAMP plays an important role in the regulation of melanogenesis in Pacific oysters. CREM is a key transcription factor in the oyster melanin synthesis pathway, which plays a crucial role in oyster melanin synthesis through a cAMP-mediated CREM-MITF-TYR axis.

Epimedin B exhibits pigmentation by increasing tyrosinase family proteins expression, activity, and stability

Epimedin B (EB) is one of the main flavonoid ingredients present in Epimedium brevicornum Maxim., a traditional herb widely used in China. Our previous study showed that EB was a stronger inducer of melanogenesis and an activator of tyrosinase (TYR). However, the role of EB in melanogenesis and the mechanism underlying the regulation remain unclear. Herein, as an extension to our previous investigation, we provide comprehensive evidence of EB-induced pigmentation in vivo and in vitro and elucidate the melanogenesis mechanism by assessing its effects on the TYR family of proteins (TYRs) in terms of expression, activity, and stability. The results showed that EB increased TYRs expression through microphthalmia-associated transcription factor-mediated p-Akt (referred to as protein kinase B (PKB))/glycogen synthase kinase 3β (GSK3β)/β-catenin, p-p70 S6 kinase cascades, and protein 38 (p38)/mitogen-activated protein (MAP) kinase (MAPK) and extracellular regulated protein kinases (ERK)/MAPK pathways, after which EB increased the number of melanosomes and promoted their maturation for melanogenesis in melanoma cells and human primary melanocytes/skin tissues. Furthermore, EB exerted repigmentation by stimulating TYR activity in hydroquinone- and N-phenylthiourea-induced TYR inhibitive models, including melanoma cells, zebrafish, and mice. Finally, EB ameliorated monobenzone-induced depigmentation in vitro and in vivo through the enhancement of TYRs stability by inhibiting TYR misfolding, TYR-related protein 1 formation, and retention in the endoplasmic reticulum and then by downregulating the ubiquitination and proteolysis processes. These data conclude that EB can target TYRs and alter their expression, activity, and stability, thus stimulating their pigmentation function, which might provide a novel rational strategy for hypopigmentation treatment in the pharmaceutical and cosmetic industries.

Natural product rhynchophylline prevents stress-induced hair graying by preserving melanocyte stem cells via the β2 adrenergic pathway suppression

Norepinephrine (NA), a stress hormone, can accelerate hair graying by binding to β2 adrenergic receptors (β2AR) on melanocyte stem cells (McSCs). From this, NA-β2AR axis could be a potential target for preventing the stress effect. However, identifying selective blockers for β2AR has been a key challenge. Therefore, in this study, advanced computer-aided drug design (CADD) techniques were harnessed to screen natural molecules, leading to the discovery of rhynchophylline as a promising compound. Rhynchophylline exhibited strong and stable binding within the active site of β2AR, as verified by molecular docking and dynamic simulation assays. When administered to cells, rhynchophylline effectively inhibited NA-β2AR signaling. This intervention resulted in a significant reduction of hair graying in a stress-induced mouse model, from 28.5% to 8.2%. To gain a deeper understanding of the underlying mechanisms, transcriptome sequencing was employed, which revealed that NA might disrupt melanogenesis by affecting intracellular calcium balance and promoting cell apoptosis. Importantly, rhynchophylline acted as a potent inhibitor of these downstream pathways. In conclusion, the study demonstrated that rhynchophylline has the potential to mitigate the negative impact of NA on melanogenesis by targeting β2AR, thus offering a promising solution for preventing stress-induced hair graying.

Metabolomic profiling between vitiligo patients and healthy subjects in plateau exhibited significant differences with those in plain

Vitiligo is the most common disorder of depigmentation, which is caused by multiple factors like metabolic abnormality, oxidative stress and the disorders of immune. In recent years, several studies have used untargeted metabolomics to analyze differential metabolites in patients with vitiligo, however, the subjects in these studies were all in plain area. In our study, multivariate analysis indicated a distinct separation between the healthy subjects from plateau and plain areas in electrospray positive and negative ions modes, respectively. Similarly, a distinct separation between vitiligo patients and healthy controls from plateau and plain areas was detected in the two ions modes. Among the identified metabolites, the serum levels of sphingosine 1-phosphate (S1P) were markedly higher in vitiligo patients compare to healthy subjects in plain and markedly higher in healthy subjects in plateau compare to those in plain. There are significant differences in serum metabolome between vitiligo patients and healthy subjects in both plateau and plain areas, as well as in healthy subjects from plateau and plain areas. S1P metabolism alteration may be involved in the pathogenesis of vitiligo.

Syringetin Promotes Melanogenesis in B16F10 Cells

Syringetin, an active compound present in red grapes, jambolan fruits, Lysimachia congestiflora, and Vaccinium ashei, is a dimethyl myricetin derivative which contains free hydroxyl groups at the C-2' and C-4' positions in ring B. Recent studies have revealed that syringetin possesses multiple pharmacological properties, such as antitumor, hepatoprotective, antidiabetic, antioxidative, and cytoprotective activities. To date, there has been no attempt to test the action of syringetin on melanogenesis. In addition, the molecular mechanism for the melanogenic effects of syringetin remains largely unknown. In this study, we investigated the effect of syringetin on melanogenesis in a murine melanoma cell line from a C57BL/6J mouse, B16F10. Our results showed that syringetin markedly stimulated melanin production and tyrosinase activity in a concentration-dependent manner in B16F10 cells. We also found that syringetin increased MITF, tyrosinase, TRP-1, and TRP-2 protein expression. Moreover, syringetin inhibited ERK and PI3K/Akt phosphorylation by stimulating p38, JNK, PKA phosphorylation levels, subsequently stimulating MITF and TRP upregulation, resulting in the activation of melanin synthesis. Furthermore, we observed that syringetin activated phosphorylation of GSK3β and β-catenin and reduced the protein level of β-catenin, suggesting that syringetin stimulates melanogenesis through the GSK3β/β-catenin signal pathway. Finally, a primary skin irritation test was conducted on the upper backs of 31 healthy volunteers to determine the irritation or sensitization potential of syringetin for topical application. The results of the test indicated that syringetin did not cause any adverse effects on the skin. Taken together, our findings indicated that syringetin may be an effective pigmentation stimulator for use in cosmetics and in the medical treatment of hypopigmentation disorders.

6-Methylcoumarin Promotes Melanogenesis through the PKA/CREB, MAPK, AKT/PI3K, and GSK3β/β-Catenin Signaling Pathways

We investigated the effects of four coumarin derivatives, namely, 6-methylcoumarin, 7-methylcoumarin, 4-hydroxy-6-methylcoumarin, and 4-hydroxy-7-methylcoumarin, which have similar structures on melanogenesis in a murine melanoma cell line from a C57BL/6J mouse called B16F10. Our results showed that only 6-methylcoumarin significantly increased the melanin synthesis in a concentration-dependent manner. In addition, the tyrosinase, TRP-1, TRP-2, and MITF protein levels were found to significantly increase in response to 6-methylcoumarin in a concentration-dependent manner. To elucidate the molecular mechanism whereby 6-methylcoumarin-induced melanogenesis influences the melanogenesis-related protein expression and melanogenesis-regulating protein activation, we further assessed the B16F10 cells. The inhibition of the ERK, Akt, and CREB phosphorylation, and conversely, the increased p38, JNK, and PKA phosphorylation activated the melanin synthesis via MITF upregulation, which ultimately led to increased melanin synthesis. Accordingly, 6-methylcoumarin increased the p38, JNK, and PKA phosphorylation in the B16F10 cells, whereas it decreased the phosphorylated ERK, Akt, and CREB expressions. In addition, the 6-methylcoumarin activated GSK3β and β-catenin phosphorylation and reduced the β-catenin protein level. These results suggest that 6-methylcoumarin stimulates melanogenesis through the GSK3β/β-catenin signal pathway, thereby affecting the pigmentation process. Finally, we tested the safety of 6-methylcoumarin for topical applications using a primary human skin irritation test on the normal skin of 31 healthy volunteers. We found that 6-methylcoumarin did not cause any adverse effects at concentrations of 125 and 250 μM. Our findings indicate that 6-methylcoumarin may be an effective pigmentation stimulator for use in cosmetics and the medical treatment of photoprotection and hypopigmentation disorders.

Creb2 involved in innate immunity by activating PpMitf-mediated melanogenesis in Pteria penguin

cAMP response element binding protein 2 (CREB2) acts as an intracellular transcriptional factor and regulates many physiological processes, including melanogenesis and melanocyte differentiation. In our previous research, the Creb2 gene has been characterized from Pteria penguin (P. penguin), but its role and regulatory mechanism in P. penguin are still unclear. In this study, first, the function of PpCreb2 in melanogenesis and innate immunity were identified. PpCreb2 silencing significantly decreased the tyrosinase activity and melanin content, indicating PpCreb2 played an important role in melanogenesis. Meanwhile, PpCreb2 silencing visibly suppressed the antibacterial activity of hemolymph supernatant, indicating that PpCreb2 was involved in innate immunity of P. penguin. Second, the PpCreb2 was confirmed to perform immune function by regulating the melanogenesis. The decreased melanin oxidation product due to PpCreb2 silencing triggered the declining of antibacterial activity of hemolymph supernatant, which then could be rescued by adding exogenous melanin oxidation products. Third, the regulation pathway of PpCreb2 involved in innate immunity was analyzed. The promoter sequence analysis of PpMitf discovered 5 conserved cAMP response element (CRE), which were specifically recognized by basic Leucine zipper domain (bZIP) of upstream activation transcription factor. The luciferase activities analysis showed that PpCreb2 could activate the CRE in PpMitf promoter via highly conserved bZIP domain and regulate the expression of PpMitf, which further regulated the PpTyr expression. Therefore, the results collectively demonstrated that PpCreb2 participated in innate immunity by activating PpMitf-mediated melanogenesis in P. penguin.

Anti-Melanogenesis Effects of a Cyclic Peptide Derived from Flaxseed via Inhibition of CREB Pathway

Linosorbs (Los) are cyclic peptides from flaxseed oil composed of the LO mixture (LOMIX). The activity of LO has been reported as being anti-cancer and anti-inflammatory. However, the study of skin protection has still not proceeded. In particular, there are poorly understood mechanisms of melanogenesis to LO. Therefore, we investigated the anti-melanogenesis effects of LOMIX and LO, and its activity was examined in mouse melanoma cell lines. The treatment of LOMIX (50 and 100 μg/mL) and LO (6.25-50 μM) suppressed melanin secretion and synthesis, which were 3-fold increased, in a dose-dependent manner, up to 95%. In particular, [1-9-NαC]-linusorb B3 (LO1) and [1-9-NαC]-linusorb B2 (LO2) treatment (12.5 and 25 μM) highly suppressed the synthesis of melanin in B16F10 cell lines up to 90%, without toxicity. LOMIX and LOs decreased the 2- or 3-fold increased mRNA levels, including the microphthalmia-associated transcription factor (MITF), Tyrosinase, tyrosinase-related protein 1 (TYRP1), and tyrosinase-related protein 2 (TYRP2) at the highest concentration (25 μM). Moreover, the treatment of 25 μM LO1 and LO2 inhibited the expression of MITF and phosphorylation of upper regulatory proteins such as CREB and PKA. Taken together, these results suggested that LOMIX and its individual LO could inhibit melanin synthesis via downregulating the CREB-dependent signaling pathways, and it could be used for novel therapeutic materials in hyperpigmentation.

Imperatorin Positively Regulates Melanogenesis through Signaling Pathways Involving PKA/CREB, ERK, AKT, and GSK3β/β-Catenin

The present study investigated the melanogenic effects of imperatorin and isoimperatorin and the underlying mechanisms of imperatorin using a mouse melanoma B16F10 model. Interestingly, treatment with 25 μM of either imperatorin or isoimperatorin, despite their structural differences, did not produce differences in melanin content and intracellular tyrosinase activity. Imperatorin also activated the expression of melanogenic enzymes, such as tyrosinase (TYR) and tyrosinase-related proteins TYRP-1 and TYRP-2. Mechanistically, imperatorin increases melanin synthesis through the cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA)/cAMP-responsive element-binding protein (CREB)-dependent upregulation of microphthalmia-associated transcription factor (MITF), which is a key transcription factor in melanogenesis. Furthermore, imperatorin exerted melanogenic effects by downregulating extracellular signal-regulated kinase (ERK) and upregulating phosphatidylinositol 3 kinase (PI3K)/protein kinase B (AKT)/glycogen synthesis kinase-3β (GSK-3β). Moreover, imperatorin increased the content of β-catenin in the cell cytoplasm and nucleus by reducing the content of phosphorylated β-catenin (p-β-catenin). Finally, we tested the potential of imperatorin in topical application through primary human skin irritation tests. These tests were performed on the normal skin (upper back) of 31 volunteers to determine whether 25 or 50 µM of imperatorin had irritation or sensitization potential. During these tests, imperatorin did not induce any adverse reactions. Taken together, these findings suggest that the regulation of melanogenesis by imperatorin can be mediated by signaling pathways involving PKA/CREB, ERK, AKT, and GSK3β/β-catenin and that imperatorin could prevent the pathogenesis of pigmentation diseases when used as a topical agent.

Capturing Genetic Diversity and Selection Signatures of the Endangered Kosovar Balusha Sheep Breed

There is a growing concern about the loss of animal genetic resources. The aim of this study was to analyze the genetic diversity and potential peculiarity of the endangered Kosovar sheep breed Balusha. For this purpose, a dataset consisting of medium-density SNP chip genotypes (39,879 SNPs) from 45 Balusha sheep was generated and compared with SNP chip genotypes from 29 individuals of a second Kosovar breed, Bardhoka. Publicly available SNP genotypes from 39 individuals of the relatively closely located sheep breeds Istrian Pramenka and Ruda were additionally included in the analyses. Analysis of heterozygosity, allelic richness and effective population size was used to assess the genetic diversity. Inbreeding was evaluated using two different methods (F_IS, F_ROH). The standardized F_ST (d_i) and cross-population extended haplotype homozygosity (XPEHH) methods were used to detect signatures of selection. We observed the lowest heterozygosity (H_O = 0.351) and effective population size (Ne₅ = 25, Ne₅₀ = 228) for the Balusha breed. The mean allelic richness levels (1.780–1.876) across all analyzed breeds were similar and also comparable with those in worldwide breeds. F_ROH estimates (0.023–0.077) were highest for the Balusha population, although evidence of decreased inbreeding was observed in F_IS results for the Balusha breed. Two Gene Ontology (GO) TERMs were strongly enriched for Balusha, and involved genes belonging to the melanogenesis and T cell receptor signaling pathways, respectively. This could result from selection for the special coat color pattern of Balusha (black head) and resistance to certain infectious diseases. The analyzed diversity parameters highlight the urgency to preserve the local Kosovar Balusha sheep as it is clearly distinguished from other sheep of Southeastern Europe, has the lowest diversity level and may harbor valuable genetic variants, e.g., for resistance to infectious diseases.

LncRNA-mRNA co-expression network revealing the regulatory roles of lncRNAs in melanogenesis in vitiligo

Vitiligo is characterized by the progressive disappearance of melanocytes, resulting in depigmentation. Long noncoding RNAs (lncRNAs) are a class of noncoding RNAs that play an essential role in the regulation of inflammation and immunity. Published reports on the expression profile of lncRNAs in vitiligo cases and the potential biological function of lncRNAs in vitiligo are lacking. We performed RNA-Seq to identify the functions of lncRNAs in vitiligo. In total, 32 upregulated lncRNAs and 78 downregulated lncRNAs were identified in skin lesions with vitiligo. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis demonstrated that mRNAs regulated by abnormally expressed lncRNAs are most relevant to melanocyte function and melanogenesis. We identified 14 aberrantly expressed lncRNAs through the co-expression pattern that regulate the melanogenesis-related genes DCT, TYR, and TYRP1. Therefore, we speculate that these hub genes may be involved in pathological mechanisms in melanocytes in vitiligo. These genes are closely related to melanogenesis in vitiligo. Abnormally expressed lncRNAs directly or indirectly act on these target genes to regulate melanogenesis. Identifying lncRNAs and clarifying the regulatory roles of the lncRNA-mRNA network may be helpful to develop novel diagnoses or treatment targets for vitiligo.