Protocatechuic Aldehyde Inhibits α-MSH-Induced Melanogenesis in B16F10 Melanoma Cells via PKA/CREB-Associated MITF Downregulation

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.

Antimelanogenic Effect of Isoquinoline Alkaloids from Plumula Nelumbinis

Plumula Nelumbinis, the green embryo of a lotus seed, is widely consumed in China as a well-known food with medicinal effects. In this study, 14 alkaloids, including 4 new and 10 known alkaloids, were isolated from it, which were elucidated by comprehensive spectroscopic analysis, and were investigated for their antimelanogenic effects in vitro and in vivo. As a result, melanogenesis in α-MSH-stimulated B16F10 cells was reduced significantly by a new compound 4 and known compound 12 at a concentration of 0.5 μg/mL, and the tyrosinase (TYR) activities were inhibited by 78.7 and 82.0% at 4 μg/mL, prior to α-arbutin (41.3%). Additionally, compounds 4 and 12 also exhibited superior antimelanogenic effects compared to α-arbutin on a zebrafish assay model at equivalent concentrations. Mechanistically, our preliminary findings suggested that compounds 4 and 12 exerted antimelanogenesis effect probably by inhibiting key proteins involved in melanin production such as microphthalmia-associated transcription factor, TYR, TRP-1, and TRP-2. The findings highlight the potential use of Plumula Nelumbinis containing compounds 4 and 12 as functional foods for treating hyperpigmentation.

Anhydrous Alum Inhibits α-MSH-Induced Melanogenesis by Down-Regulating MITF via Dual Modulation of CREB and ERK

Melanogenesis, the intricate process of melanin synthesis, is central to skin pigmentation and photoprotection and is regulated by various signaling pathways and transcription factors. To develop potential skin-whitening agents, we used B16F1 melanoma cells to investigate the inhibitory effects of anhydrous alum on melanogenesis and its underlying molecular mechanisms. Anhydrous alum (KAl(SO4)2) with high purity (>99%), which is generated through the heat-treatment of hydrated alum (KAl(SO4)2·12H2O) at 400 °C, potentiates a significant reduction in melanin content without cytotoxicity. Anhydrous alum downregulates the master regulator of melanogenesis, microphthalmia-associated transcription factor (MITF), which targets key genes involved in melanogenesis, thereby inhibiting α-melanocyte-stimulating hormone (α-MSH)-induced melanogenesis. Phosphorylation of the cAMP response element-binding protein, which acts as a co-activator of MITF gene expression, is attenuated by anhydrous alum, resulting in compromised MITF transcription. Notably, anhydrous alum promoted extracellular signal-regulated kinase phosphorylation, leading to the impaired nuclear localization of MITF. Overall, these results demonstrated the generation and mode of action of anhydrous alum in B16F1 cells, which constitutes a promising option for cosmetic or therapeutic use.

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.

Acenocoumarol, an Anticoagulant Drug, Prevents Melanogenesis in B16F10 Melanoma Cells

Hyperpigmentation can occur in abnormal skin conditions such as melanomas, as well as in conditions including melasma, freckles, age spots, seborrheic keratosis, and café-au-lait spots (flat brown spots). Thus, there is an increasing need for the development of depigmenting agents. We aimed to repurpose an anticoagulant drug as an effective ingredient against hyperpigmentation and apply cosmeceutical agents. In the present study, the anti-melanogenic effects of two anticoagulant drugs, acenocoumarol and warfarin, were investigated. The results showed that both acenocoumarol and warfarin did not cause any cytotoxicity and resulted in a significant reduction in intracellular tyrosinase activity and melanin content in B16F10 melanoma cells. Additionally, acenocoumarol inhibits the expression of melanogenic enzymes such as tyrosinase, tyrosinase-related protein (TRP)-1, and TRP-2, suppressing melanin synthesis through a cAMP-dependent, protein kinase (PKA)-dependent downregulation of microphthalmia-associated transcription factor (MITF), a master transcription factor in melanogenesis. Furthermore, anti-melanogenic effects were exerted by acenocoumarol through downregulation of the p38 and JNK signaling pathway and upregulation of extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt)/glycogen synthesis kinase-3β (GSK-3β) cascades. In addition, the β-catenin content in the cell cytoplasm and nucleus was increased by acenocoumarol through a reduction in the phosphorylated β-catenin (p-β-catenin content). Finally, we tested the potential of acenocoumarol for topical applications by conducting primary human skin irritation tests. Acenocoumarol did not induce any adverse reactions during these tests. Based on the results, it can be concluded that acenocoumarol regulates melanogenesis through various signaling pathways such as PKA, MAPKs, PI3K/Akt/GSK-3β, and β-catenin. These findings suggest that acenocoumarol has the potential to be repurposed as a drug for treating hyperpigmentation symptoms and could provide new insights into the development of therapeutic approaches for hyperpigmentation disorders.

Structure Characterization and Antihypertensive Effect of an Antioxidant Peptide Purified from Alcalase Hydrolysate of Velvet Antler

Recently, interest in food-derived bioactive peptides as promising ingredients for the prevention and improvement of hypertension is increasing. The purpose of this study was to determine the structure and antihypertensive effect of an antioxidant peptide purified from velvet antler in a previous study and evaluate its potential as a various bioactive peptide. Molecular weight (MW) and amino acid sequences of the purified peptide were determined by quadrupole time-of-flight electrospray ionization mass spectroscopy. The angiotensin I-converting enzyme (ACE) inhibition activity of the purified peptide was assessed by enzyme reaction methods and in silico molecular docking analysis to determine the interaction between the purified peptide and ACE. Also, antihypertensive effect of the purified peptide in spontaneously hypertensive rats (SHRs) was investigated. The purified antioxidant peptide was identified to be a pentapeptide Asp-Asn-Arg-Tyr-Tyr with a MW of 730.31 Da. This pentapeptide showed potent inhibition activity against ACE (IC₅₀ value, 3.72 μM). Molecular docking studies revealed a good and stable binding affinity between purified peptide and ACE and indicated that the purified peptide could interact with HOH2570, ARG522, ARG124, GLU143, HIS387, TRP357, and GLU403 residues of ACE. Furthermore, oral administration of the pentapeptide significantly reduced blood pressure in SHRs. The pentapeptide derived from enzymatic hydrolysate of velvet antler is an excellent ACE inhibitor. It might be effectively applied as an animal-based functional food ingredient.

Ligand fishing of monoamine oxidase B inhibitors from Platycodon grandiflorus (Jacq.) A.DC. roots by the enzyme functionalised magnetic nanoparticles

INTRODUCTION

As a famous traditional Chinese medicine, roots of Platycodon grandiflorus (Jacq.) A.DC. have shown multiple effects against neurodegenerative diseases. To investigate the components against Parkinson's disease (PD), the roots of P. grandiflora were selected as the research subject.

OBJECTIVE

Screening and identifying of monoamine oxidase B (MAO-B) inhibitors from the roots of P. grandiflorum via enzyme functionalised magnetic nanoparticles (MNPs)-based ligand fishing combined with high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis.

METHOD

MAO-B functionalised MNPs have been synthesised for screening MAO-B inhibitors from the roots of P. grandiflorum. The ligands were identified by HPLC-MS and nuclear magnetic resonance (NMR) analysis, and their anti-PD activity was evaluated via MAO-B inhibition assay and cell viability assay in vitro.

RESULTS

Two MAO-B inhibitors were fished out and identified by HPLC-MS as protocatechuic aldehyde (1) and coumarin (2), with the half maximal inhibitory concentrations of 28.54 ± 0.39 and 25.39 ± 0.29 μM, respectively. Among them, 1 could also significantly increase the viability of 6-hydroxydopamine-damaged PC12 cells.

CONCLUSION

The results are helpful to elucidate the anti-PD activity of the plant, and the ligand fishing method has shown good potential in discovery of MAO-B inhibitors.

Atraric Acid Ameliorates Hyperpigmentation through the Downregulation of the PKA/CREB/MITF Signaling Pathway

Atraric acid (AA) is derived from lichens and is widely used in perfumes for its desirable scent. It has been reported as having anti-inflammatory and antioxidant activity. Hyperpigmentation is the underlying cause of a variety of dermatological diseases that have a significant impact on patients' quality of life and are frequently difficult to treat. This study aimed to explore the inhibitory effects of AA on hyperpigmentation in vitro and in vivo and its potential molecular mechanisms. The cytological results revealed that at a dose of 250 μM, AA may reduce melanin content and tyrosinase levels without causing cytotoxicity. Furthermore, the expression of melanocortin-1 receptor (MC1R), phosphorylated protein kinase A (pPKA) and phosphorylated cAMP response element binding protein (pCREB) were downregulated in AA-administrated cells. In vivo, histological analysis showed that AA could inhibit melanin production and tyrosinase activity, and 3% AA had the best activity, with almost no side effects. Furthermore, the results of Western blot analysis and RT-PCR suggested that AA may suppress the mRNA transcription of microphthalmia-associated transcription factor (MITF) protein and tyrosine protease by decreasing the expression of MC1R, consequently decreasing the phosphorylation of PKA and CREB. Finally, the MC1R inhibitor MSG606 verified the hypothesis that AA suppresses melanin formation by downregulating the PKA/CREB/MITF signaling pathway. Taken together, our study offers valuable information for the development of AA as a possible ingredient in skin-lightening cosmeceuticals and hyperpigmentation inhibitors.

Heat-Killed Lacticaseibacillus paracasei Ameliorated UVB-Induced Oxidative Damage and Photoaging and Its Underlying Mechanisms

Ultraviolet B (UVB) radiation is a major environmental causative factor of skin oxidative damage and photoaging. Lacticaseibacillus paracasei is a well-known probiotic strain that can regulate skin health. The present study investigated the effects of heat-killed Lacticaseibacillus paracasei (PL) on UVB linked oxidative damage and photoaging in skin cells (Normal human dermal fibroblast (NHDF) cells and B16F10 murine melanoma cells). Results demonstrated that: (1) PL prevented UVB-induced cytotoxicity relating to decreased DNA damage in NHDF and B16F10 cells; (2) PL alleviated UVB-induced oxidative damage through increasing GSH content, as well as antioxidant enzyme activities and mRNA levels (except MnSOD activity and mRNA levels as well as CAT mRNA level) relating to the activation of Sirt1/PGC-1α/Nrf2 signaling in NHDF cells; (3) PL attenuated UVB-induced photoaging was noticed with a decrease in the percentage of SA-β-gal positive cells in NHDF cells model. Moreover, PL attenuated UVB-induced photoaging through exerting an anti-wrinkling effect by enhancing the type I collagen level relating to the inhibition (JNK, p38)/(c-Fos, c-Jun) of signaling in NHDF cells, and exerting an anti-melanogenic effect by suppressing tyrosinase and TYRP-1 activity and/or expressions relating to the inhibition of PKA/CREB/MITF signaling in B16F10 cells. In conclusion, PL could ameliorate UVB-induced oxidative damage and photoaging. Therefore, PL may be a potential antioxidant and anti-photoaging active ingredient for the cosmetic industry.

Response of Thymus lotocephalus In Vitro Cultures to Drought Stress and Role of Green Extracts in Cosmetics

The impact of drought stress induced by polyethylene glycol (PEG) on morphological, physiological, (bio)chemical, and biological characteristics of Thymus lotocephalus López and Morales shoot cultures have been investigated, as well as the potential of iron oxide nanoparticles, salicylic acid, and methyl jasmonate (MeJA) as alleviating drought stress agents. Results showed that PEG caused oxidative stress in a dose-dependent manner, raising H₂O₂ levels and reducing shoots’ growth, photosynthetic pigment contents, and phenolic compounds production, especially phenolic acids, including the major compound rosmarinic acid. Moreover, Fourier Transform Infrared Spectra analysis revealed that PEG treatment caused changes in shoots’ composition, enhancing terpenoids biosynthesis. PEG also decreased the biological activities (antioxidant, anti-tyrosinase, and photoprotective) of the eco-friendly extracts obtained with a Natural Deep Eutectic Solvent. MeJA was the most efficient agent in protecting cells from oxidative damage caused by drought, by improving the biosynthesis of phenolics, like methyl 6-O-galloyl-β-D-glucopyranoside and salvianolic acids, as well as improving the extracts’ antioxidant activity. Altogether, the obtained results demonstrated a negative impact of PEG on T. lotocephalus shoots and an effective role of MeJA as a mitigating agent of drought stress. Additionally, extracts showed a good potential to be used in the cosmetics industry as skincare products.

Vegetable-derived indole enhances the melanoma-treating efficacy of chemotherapeutics

Food-drug interaction is an important but overlooked issue. For example, little is known concerning whether or not the chemotherapy of cancers is affected by the well-defined dietary chemicals such as 2-(indol-3-ylmethyl)-3,3'-diindolylmethane (LTr1) derived from daily consumed cruciferous vegetables. This work, inspired by the described melanogenesis reduction by certain indoles, presents that LTr1 mitigates the melanogenesis and thus potentiates the in vitro and in vivo anti-melanoma effectiveness of different chemotherapeutic agents including dacarbazine, vemurafenib, and sorafenib. In B16 melanoma cells, LTr1 was shown to inhibit the melanogenesis by acting towards the regulatory (R) subunit of protein kinase A (PRKAR1a) associated with the phosphorylation of cAMP-response element binding protein (CREB). This allows LTr1 to reduce the expression of melanogenesis-related enzymes such as tyrosinase (TYR), tyrosinase-related protein 1 (TYRP1), and tyrosinase-related protein 2 (TYRP2). Furthermore, LTr1 was addressed to bind to the aryl hydrocarbon receptor (AhR) and up-regulate the expression of CYP1A1 encoding cytochrome P450 1A1, leading to the escalation of reactive oxygen species (ROS) level. The increased ROS generation promotes the cysteine-to-cystine transformation to inhibit the pheomelanogenesis in melanomas. Collectively, the work identifies LTr1 as a new melanogenesis inhibitor that modulates the PKA/CREB/MITF and AhR/CYP1A1/ROS pathways, thereby providing a new option for (re)sensitizing melanomas to chemotherapeutics.

Silencing of Rab23 by siRNA inhibits ultraviolet B-induced melanogenesis via downregulation of PKA/CREB/MITF

Recent investigations have shown that the Rab family of GTPases is associated with all aspects of melanogenesis. However, the effect of Rab23, which localizes to the plasma membrane and regulates the endocytic pathway within eukaryotic cells, in melanogenesis has not been reported. To understand the role of Rab23 in UVB-induced melanogenesis, we evaluated changes in the level of melanin, activity of tyrosinase, and levels of melanogenesis-related proteins such as microphthalmia transcription factor and tyrosinase-related protein-1 (TRP-1) and the melanosome transport-related protein complex Rab27a-melanophilin-myosin Va after the downregulation of Rab23 in B16F10 and SK-MEL-2 cells with or without UVB irradiation. Our results showed that downregulating Rab23 reduced the melanin level and tyrosinase activity and inhibited the expression of proteins involved in UVB-induced melanogenesis. Rab23 colocalized with mature melanosomes marked with TRP-1. Furthermore, downregulating Rab23 induced the abnormal accumulation of melanosomes around the nucleus. We demonstrated that the downregulation of Rab23 inhibited melanin synthesis and melanosome transport by decreasing the PKA/CREB/MITF pathway, which is the key regulator of UVB-induced melanogenesis.

Oxidative Transformations of 3,4-Dihydroxyphenylacetaldehyde Generate Potential Reactive Intermediates as Causative Agents for Its Neurotoxicity

Neurogenerative diseases, such as Parkinson’s disease, are associated, not only with the selective loss of dopamine (DA), but also with the accumulation of reactive catechol-aldehyde, 3,4-dihydroxyphenylacetaldehyde (DOPAL), which is formed as the immediate oxidation product of cytoplasmic DA by monoamine oxidase. DOPAL is well known to exhibit toxic effects on neuronal cells. Both catecholic and aldehyde groups seem to be associated with the neurotoxicity of DOPAL. However, the exact cause of toxicity caused by this compound remains unknown. Since the reactivity of DOPAL could be attributed to its immediate oxidation product, DOPAL-quinone, we examined the potential reactions of this toxic metabolite. The oxidation of DOPAL by mushroom tyrosinase at pH 5.3 produced conventional DOPAL-quinone, but oxidation at pH 7.4 produced the tautomeric quinone-methide, which gave rise to 3,4-dihydroxyphenylglycolaldehyde and 3,4-dihydroxybenzaldehyde as products through a series of reactions. When the oxidation reaction was performed in the presence of ascorbic acid, two additional products were detected, which were tentatively identified as the cyclized products, 5,6-dihydroxybenzofuran and 3,5,6-trihydroxybenzofuran. Physiological concentrations of Cu(II) ions could also cause the oxidation of DOPAL to DOPAL-quinone. DOPAL-quinone exhibited reactivity towards the cysteine residues of serum albumin. DOPAL-oligomer, the oxidation product of DOPAL, exhibited pro-oxidant activity oxidizing GSH to GSSG and producing hydrogen peroxide. These results indicate that DOPAL-quinone generates several toxic compounds that could augment the neurotoxicity of DOPAL.