Local Epidermal Endocrine Estrogen Protects Human Melanocytes against Oxidative Stress, a Novel Insight into Vitiligo Pathology

Molecular mechanism of vitiligo treatment by bailing tablet based on network pharmacology and molecular docking

BACKGROUND

Bailing tablet, a patent Chinese medicine, is widely used to treat vitiligo in China. However, the underlying mechanism of this combined drug in treating vitiligo still remains unclear.

OBJECTIVE

This study aimed to investigate the pharmacological mechanism of bailing tablet in the prevention and treatment of vitiligo using network pharmacology and molecular docking.

METHODS

Genetic data of vitiligo and normal people were obtained by gene expression omnibus (GEO) DataSets database and GEO difference analysis was conducted to obtain differential genes. The main active compounds and corresponding target genes of bailing tablet were collected from Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform. Combined with the results of GEO difference analysis, the main compounds and corresponding target genes of bailing tablet in the treatment of vitiligo were screened. The network diagram of "traditional Chinese medicine compound target" was constructed by Cytoscape software. According to the differential genes, the core targets with potential therapeutic effect were searched, the protein-protein interaction network was constructed, and the key proteins were explored by topological analysis (CytoNCA). Meanwhile, the core targets were analyzed by biological process (gene ontology) and signal pathway (Kyoto encyclopedia of genes and genomes) function enrichment. Molecular docking technology was adopted to verify the combination of main components and core targets.

RESULTS

A total of 170 active compounds and 1777 prediction targets were screened from 11 traditional Chinese medicines of bailing tablet, of which 65 active components and 68 related prediction targets were closely related to vitiligo. A total of 320 key proteins were obtained by analyzing the topological characteristics of the protein-protein interaction network, mainly including neurotrophic receptor tyrosine kinase 1, tumor protein P53, cullin 3, estrogen receptor 1, etc. The main biological processes involve oxidative stress response, cell response to reactive oxygen species, and reactive oxygen species metabolism. Bailing tablet treats vitiligo mainly by regulating immune inflammation, apoptosis, and autophagy, which involves phosphatidylinositol-4,5-bisphosphate 3-kinase Akt signal pathway, mitogen-activated protein kinase signal pathway, Janus kinase signal transducer and activator of transcription signal pathway, melanin production, and helper T cell (Th)1, Th2, and Th17 differentiation pathway, etc. Molecular docking results showed that the main components could bind to the target protein well.

CONCLUSIONS

Based on network pharmacology and molecular docking, the mechanism of bailing tablet in the treatment of vitiligo through multicomponent, multitarget, and multichannel was deeply explored.

Oxidative Stress in Metabolic and Endocrine Diseases: Basic and Translational Aspects

The aim of this Special Issue is to highlight oxidative stress (OS) as a mechanism underlying a major risk factor for several human diseases [...]

Surgical procedures and innovative approaches for vitiligo regenerative treatment and melanocytorrhagy

Surgical treatments for vitiligo are a safe and effective treatment modality for select patients with vitiligo. Many techniques of vitiligo surgery exist, each with unique advantages and disadvantages. We reviewed the various surgical therapies and innovative approaches for vitiligo regenerative treatment reported in the literature. Surgical therapies can be subdivided into tissue grafting methods and cellular grafting methods. Tissue grafting methods mainly include mini punch grafts, suction blister roof grafts, and hair follicle grafts. Cellular grafting methods include cultured and non-cultured treatments. The efficacy needs to be improved largely due to the poor proliferation and quality of the autologous melanocytes. Rho-associated protein kinase inhibitor enhances primary melanocyte culture proliferation from vitiligo patients to prevent apoptosis. Innovative approaches using stem cell methods could prove invaluable in developing a novel cell therapy for patients suffering from vitiligo. We succeeded in inducing melanin pigmentation in mice skin in vivo using our human induced pluripotent stem cell-derived melanocytes. In addition, we reviewed melanocytorrhagy, detachment and transepidermal loss of melanocytes, and melanocyte-related adhesion molecules. These adhesion molecules include epithelial cadherin, discoidin domain receptor tyrosine kinase 1, glycoprotein non-metastatic melanoma protein B, macrophage migration inhibiting factor, 17β-hydroxysteroid dehydrogenase 1, and E26 transformation-specific 1.

GPNMB Extracellular Fragment Protects Melanocytes from Oxidative Stress by Inhibiting AKT Phosphorylation Independent of CD44

Glycoprotein non-metastatic melanoma protein B (GPNMB) is a type I transmembrane glycoprotein that plays an important role in cancer metastasis and osteoblast differentiation. In the skin epidermis, GPNMB is mainly expressed in melanocytes and plays a critical role in melanosome formation. In our previous study, GPNMB was also found to be expressed in skin epidermal keratinocytes. In addition, decreased GPNMB expression was observed in the epidermis of lesional skin of patients with vitiligo. However, the exact role of keratinocyte-derived GPNMB and its effect on vitiligo is still unknown. In this study, we demonstrated that GPNMB expression was also decreased in rhododendrol-induced leukoderma, as seen in vitiligo. The extracellular soluble form of GPNMB (sGPNMB) was found to protect melanocytes from cytotoxicity and the impairment of melanogenesis induced by oxidative stress. Furthermore, the effect of rGPNMB was not altered by the knockdown of CD44, which is a well-known receptor of GPNMB, but accompanied by the suppressed phosphorylation of AKT but not ERK, p38, or JNK. In addition, we found that oxidative stress decreased both transcriptional GPNMB expression and sGPNMB protein expression in human keratinocytes. Our results suggest that GPNMB might provide novel insights into the mechanisms related to the pathogenesis of vitiligo and leukoderma.

A Lower Irradiation Dose of 308 nm Monochromatic Excimer Light Might Be Sufficient for Vitiligo Treatment: A Novel Insight Gained from In Vitro and In Vivo Analyses

A 308 nm monochromatic excimer light (MEL) is widely used to treat patients with vitiligo. However, dose optimization still needs to be clarified. This study aimed to obtain objective evidence regarding various doses of MEL irradiation, induced cell level changes in vitro, and skin level alterations in vivo. Cultured human keratinocytes were irradiated with MEL using various doses. After irradiation at low doses, stem cell factor, endothelin-1, and glycoprotein nonmetastatic melanoma protein B, factors that activate and protect melanocytes, were found to be significantly elevated in keratinocytes. After irradiation using medium and high doses, inflammatory cytokines were induced. The amount of ATP released and the level of inflammasome activation, which are known to be related to interleukin-1β activation, were also increased. The back skin of guinea pigs and mice were irradiated with MEL at varying doses. After irradiation, an increase of epidermal melanin and epidermal melanocytes was confirmed, using the minimal erythemal dose or less. In rhododendrol-induced leukoderma guinea pigs, a much lower dose of MEL irradiation was effective, when compared with the effective dose for control guinea pigs. Our results suggest that a lower irradiation dose of MEL might be sufficient and more suitable for repigmentation in vitiligo treatment.

Ginsenoside Rk1 protects human melanocytes from H2O2‑induced oxidative injury via regulation of the PI3K/AKT/Nrf2/HO‑1 pathway

Vitiligo is a cutaneous depigmentation disorder caused by melanocyte injury or aberrant functioning. Oxidative stress (OS) is considered to be a major cause of the onset and progression of vitiligo. Ginsenoside Rk1 (RK1), a major compound isolated from ginseng, has antioxidant activity. However, whether RK1 can protect melanocytes against oxidative injury remains unknown. The aim of the present study was to investigate the potential protective effect of RK1 against OS in the human PIG1 melanocyte cell line induced with hydrogen peroxide (H₂O₂), and to explore its underlying mechanism. PIG1 cells were pretreated with RK1 (0, 0.1, 0.2 and 0.4 mM) for 2 h followed by exposure to 1.0 mM H₂O₂ for 24 h. Cell viability and apoptosis were determined with Cell Counting Kit‑8 and flow cytometry assays, respectively. The activity levels of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH‑Px) were analyzed using ELISA kits. Protein expression levels, including Bax, caspase‑3, Bcl‑2, phosphorylated‑AKT, AKT, nuclear factor erythroid 2‑related factor 2 (Nrf2), heme oxygenase‑1 (HO‑1), cytosolic Nrf2 and nuclear Nrf2, were analyzed using western blot analysis. In addition, the expression and localization of Nrf2 were detected by immunofluorescence. RK1 treatment significantly improved cell viability, reduced the apoptotic rate and increased the activity levels of SOD, CAT and GSH‑Px in the PIG1 cell line exposed to H₂O₂. In addition, RK1 treatment notably induced Nrf2 nuclear translocation, increased the protein expression levels of Nrf2 and HO‑1, and the ratio of phosphorylated‑AKT to AKT in the PIG1 cells exposed to H₂O₂. Furthermore, LY294002 could reverse the protective effect of RK1 in melanocytes against oxidative injury. These data demonstrated that RK1 protected melanocytes from H₂O₂‑induced OS by regulating Nrf2/HO‑1 protein expression, which may provide evidence for the application of RK1 for the treatment of vitiligo.

Morphological Alterations and Increased S100B Expression in Epidermal Langerhans Cells Detected in Skin from Patients with Progressive Vitiligo

The role of Langerhans cells (LCs) in vitiligo pathogenesis remains unclear, with published studies reporting contradictory results regarding the quantity of LCs and no data on the features of LCs in vitiligo. Here, we aimed to analyze the presence, density, and morphological features of LCs in the epidermis of patients with vitiligo. Skin biopsies were stained for LCs using anti-CD1a/anti-langerin antibodies and analyzed by immunocytochemistry with light and electron microscopy. Compared with healthy controls, we detected significantly increased numbers of epidermal LCs in lesional skin from vitiligo in the progressive state. These LCs exhibited striking morphological alterations, including an elevated number of dendrites, with increased length and more branches than dendrites from controls. Ultrastructure examination via immuno-electron microscopy revealed markedly reduced Birbeck granules (BGs) and shorter BG rods in LCs from progressive vitiligo, with higher expression of langerin. Additionally, expression of S100B, the activity biomarker of vitiligo, was increased in these LCs. This work provides new insight on the cellular composition of LCs in vitiliginous skin, revealing altered morphology and increased LC numbers, with elevated S100B expression. Our data suggest LCs might play a critical role in vitiligo pathogenesis and thus may represent a novel therapeutic target for this disease.