Role of kinin receptors in skin pigmentation.

Previous studies have shown that all kinin system is constitutively expressed in the normal and inflamed skin, with a potential role in both physiological and pathological processes. However, the understanding regarding the involvement of the kinin system in skin pigmentation and pigmentation disorders remains incomplete. In this context, the present study was designed to determine the role of kinins in the Monobenzone (MBZ)-induced vitiligo-like model. Our findings showed that MBZ induces higher local skin depigmentation in kinin receptors knockout mice (KOB1R, KOB2R and KOB1B2R) than in wild type (WT). Remarkably, lower levels of melanin content and reduced ROS generation were detected in KOB1R and KOB2R mice treated with MBZ. In addition, both KOB1R and KOB2R show increased dermal cell infiltrate in vitiligo-like skin, when compared to WT-MBZ. Additionally, lack of B1R was associated with greater skin accumulation of IL-4, IL-6, and IL-17 by MBZ, while KOB1B2R presented lower levels of TNF and IL-1. Of note, the absence of both kinin B1 and B2 receptors demonstrates a protective effect by preventing the increase in polymorphonuclear and mononuclear cell infiltrations, as well as inflammatory cytokine levels induced by MBZ. In addition, in vitro assays confirm that B1R and B2R agonists increase intracellular melanin synthesis, while bradykinin significantly enhanced extracellular melanin levels and proliferation of B16F10 cells. Our findings highlight that the lack of kinin receptors caused more severe depigmentation in the skin, as well as genetic deletion of both B1/B2 receptors seems to be linked with changes in levels of constitutive melanin levels, suggesting the involvement of kinin system in crucial skin pigmentation pathways.

Transcutaneous Auricular Vagus Nerve Stimulation Alleviates Monobenzone-Induced Vitiligo in Mice.

Vitiligo is a complex skin disorder that involves oxidative stress and inflammatory responses and currently lacks a definitive cure. Transcutaneous auricular vagus nerve stimulation (taVNS) is a noninvasive method for targeting the auricular branch of the vagus nerve and has gained widespread attention for potential intervention in the autonomic nervous system. Although previous research has suggested that vagus nerve stimulation can potentially inhibit inflammatory responses, its specific role and mechanisms in vitiligo treatment remain unknown. This study aimed to explore the therapeutic effects of taVNS in a mouse model of vitiligo induced by monobenzone. Initially, a quantitative assessment of the treatment effects on vitiligo mice was conducted using a scoring system, revealing that taVNS significantly alleviated symptoms, particularly by reducing the depigmented areas. Subsequent immunohistochemical analysis revealed the impact of taVNS treatment on melanocyte granules, mitigating pigment loss in the skin of monobenzone-induced vitiligo mice. Further analysis indicated that taVNS exerted its therapeutic effects through multiple mechanisms, including the regulation of oxidative stress, enhancement of antioxidant capacity, promotion of tyrosine synthesis, and suppression of inflammatory responses. The conclusions of this study not only emphasize the potential value of taVNS in vitiligo therapy, but also lay a foundation for future research into the mechanisms and clinical applications of taVNS.

Restraint stress promotes monobenzone-induced depigmentation in mice via the activation of glucocorticoid receptor/macrophage migration inhibitory factor signaling pathway.

Psychological stress triggers onset and development of vitiligo in humans. However, the mechanism of psychological stress on vitiligo remains unclear. The study aims to investigate whether psychological stress promotes vitiligo and explore the underlying mechanism. A depigmentation mouse model induced by applying a skin-bleaching reagent monobenzone to dorsal skin and an in vitro HaCaT keratinocyte death model induced by monobenzone were employed to explore the effect of restraint stress, which mimics psychological stress, on depigmentation. The results indicated that restraint stress promoted vitiligo-related depigmentation, vacuolisation, spongiosis, CD8+ T lymphocyte infiltration, and loss of melanocytes in the skin. Restraint stress activated cutaneous NLR family containing pyrin domain protein 3 (NLRP3) inflammasome. In addition, restraint stress aggravated anxiety-like behaviors and increased levels of macrophage migration inhibitory factor (MIF) and corticosterone in the circulation, accompanied with decreasing the expression of cutaneous 8-oxoguanine DNA glycosylase (OGG1) in depigmentation mice. In vitro experiments demonstrated that activation of glucocorticoid receptor (GR) by cortisol upregulated NLRP3 expression dependent on MIF, and directly decreased the transcription of OGG1. Blockade of MIF reversed the NLRP3 signal in restraint stress-induced depigmentation mice. In conclusion, restraint stress promotes vitiligo-related depigmentation in mice via the activation of GR/MIF signaling pathway. The findings provide a theoretical basis for prevention and treatments of vitiligo with therapies of targeting GR, MIF, and OGG1.

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.

Identification of Monobenzone as a Novel Potential Anti-Acute Myeloid Leukaemia Agent That Inhibits RNR and Suppresses Tumour Growth in Mouse Xenograft Model.

Acute myeloid leukaemia (AML) is one of the most common types of haematopoietic malignancy. Ribonucleotide reductase (RNR) is a key enzyme required for DNA synthesis and cell proliferation, and its small subunit RRM2 plays a key role for the enzymatic activity. We predicted monobenzone (MB) as a potential RRM2 target compound based on the crystal structure of RRM2. In vitro, MB inhibited recombinant RNR activity (IC50 = 0.25 µM). Microscale thermophoresis indicated that MB inhibited RNR activity by binding to RRM2. MB inhibited cell proliferation (MTT IC50 = 6-18 µM) and caused dose-dependent DNA synthesis inhibition, cell cycle arrest, and apoptosis in AML cells. The cell cycle arrest was reversed by the addition of deoxyribonucleoside triphosphates precursors, suggesting that RNR was the intracellular target of the compound. Moreover, MB overcame drug resistance to the common AML drugs cytarabine and doxorubicin, and treatment with the combination of MB and the Bcl-2 inhibitor ABT-737 exerted a synergistic inhibitory effect. Finally, the nude mice xenografts study indicated that MB administration produced a significant inhibitory effect on AML growth with relatively weak toxicity. Thus, we propose that MB has the potential as a novel anti-AML therapeutic agent in the future.

Monobenzone, a Novel and Potent KDM1A Inhibitor, Suppresses Migration of Gastric Cancer Cells.

Lysine-specific demethylase1 (KDM1A) is generally highly expressed in various cancer tissues, and promotes the initiation and development of cancers via diverse cellular signaling pathways. Therefore, KDM1A is a promising drug target in many cancers, and it is crucial to find effective KDM1A inhibitors, while none of them has entered into market. With the help of compound library, monobenzone, a local depigmentor using as a treating over-pigmentation in clinic, was characterized as an effective KDM1A inhibitor (IC50 = 0.4507 µM), which may competitively inhibit KDM1A reversibly. Further cellular study confirmed that monobenzone could inhibit the proliferation of gastric cancer cell lines MGC-803 and BGC-823 with IC50 as 7.82 ± 0.55 µM and 6.99 ± 0.51 µM, respectively, and erase the substrate of KDM1A, H3K4me1/2 and H3K9 me2, and inhibit the migration of gastric cancer cell by reversing epithelial-mesenchymal transition (EMT). As the structure of monobenzone is very simple and small, this study provides a novel backbone for the further optimization of KDM1A inhibitor and gives monobenzone potential new application.

Therapeutic effects of iNOS inhibition against vitiligo in an animal model.

Nitric oxide (NO) is involved in several biological processes, but its role in human melanogenesis and vitiligo need further studies. Previous studies revealed that exposure to UVA and UVB were capable of the inducing nitric oxide production in keratinocytes and melanocytes through the activation of constitutive nitric oxide synthase, whereas inducible nitric oxide synthase overexpression has been reported to play an important role in hyperpigmentary disorders. The aim of this study was to evaluate iNOS inhibitor aminoguanidine (AG) as a therapeutic agent in our mouse model of vitiligo. In this study, male C57BL/6J Ler-vit/vit mice were purchased to evaluate the effect of iNOS inhibitor (aminoguanidine) (50 and 100 mg/kg) and L-arginine (100 mg/kg) in a mouse model of vitiligo induced by monobenzone 40%. Moreover, we used phototherapy device to treat the mice with NBUVB as a gold standard.The findings revealed that monobenzone was capable of inducing depigmentation after 6 weeks. However, aminoguanidine in combination with monobenzone was decrease the effect of monobenzone, while L-arginine play a key role in promoting the effect of monobenzone (P<0.001). Based on the phototherapy, the efficacy of phototherapy significantly increased by adding L-arginine (P<0.05). Taken together, we suggest that iNOS inhibitor can be a novel treatment for the prevention and treatment of vitiligo by combination of NBUVB therapy, furthermore; NO agents like L-arginine could also increase the effectiveness of phototherapy. Taken together, this pilot study showed significant repigmentation of vitiligous lesions treated with iNOS inhibitor plus NBUVB therapy, where other aspect including expression of an inducible iNOS, NO and TNF levels remained to be evaluated in mice model.

The Therapeutic Effects of Baicalin on Vitiligo Mice.

Vitiligo is a commom disease of skin. Its pathogenesis is complex, resulting in the incapacity to find a targeted cure. Baicalin, which is isolated from Scutellariae radix, has been known to exhibit a number of pharmacological effects on autoimmune diseases. In this study, we explored the effects of Baicalin on the recovery of vitiligo stimulated by monophenylketone in mice. We observed that Baicalin slowed down the progression of depigmentation, decreased the incidence of depigmentation, and reduced the area of depigmentation. Moreover, reflectance confocal microscopy (RCM) shown that Baicalin increased the epidermal melanocytes in depigmented skin. Baicalin decreased CD8 + T cell infiltration in mice skin, and decreased the expression of CXCL10 and CXCR3. Baicalin significantly decreased the levels of serum cytokine (interleukin [IL]-6, tumor necrosis factor [TNF]-α, interferon-γ [IFN-γ], and IL-13). Collectively, these data suggest that Baicalin play an important role in the occurrence and development of vitiligo.

Chemical-Induced Vitiligo.

Chemical-induced depigmentation of the skin has been recognized for more than 75 years, first as an occupational hazard but then extending to those using household commercial products as common as hair dyes. Since their discovery, these chemicals have been used therapeutically in patients with severe vitiligo to depigment their remaining skin and improve their appearance. Because chemical-induced depigmentation is clinically and histologically indistinguishable from nonchemically induced vitiligo, and because these chemicals appear to induce melanocyte autoimmunity, this phenomenon should be known as "chemical-induced vitiligo," rather than less accurate terms that have been previously used.

Manejo despigmentante de vitiligo generalizado con monobenzil eter de hidroquinona / Depigmenting management of generalized vitiligo with hydroquinone monobenzyl ether

El vitiligo es una patología crónica, recidivante y difícil de tratar. El objetivo primario del tratamiento es inducir la repigmentación, sin embargo, en casos extensos refractarios a tratamiento, se puede realizar despigmentación para corregir la discromía. Dentro de los tratamientos despigmentantes en vitiligo, a la fecha el único aprobado por la FDA es el Monobenzil éter de hidroquinona (monobenzona). Se expone el caso de una paciente con vitiligo extenso y refractario a tratamiento que fue manejado con monobenzona. El resultado fue exitoso durante tiempo prolongado, con recaída parcial al suspender el medicamento. La recaída remitió con el reinicio de la monobenzona. Sin nueva recaída actualmente con tratamiento de mantención 3v/semana. La monobenzona induce acromía secundaria a necrosis de los melanocitos. Se requiere su uso 1 a 2 veces al día por 6-12 meses para lograr la despigmentación. En pacientes adecuadamente seleccionados, es una alternativa válida para el manejo del vitiligo. Se presenta un caso exitoso de despigmentación con monobenzona. Actualmente, la paciente está muy satisfecha con los resultados.

Vitiligo is a chronic, recurrent pathology, difficult to treat. The primary goal of treatment is to induce repigmentation, however, in extensive cases refractory to treatment depigmentation of surrounding skin may be performed to correct the cosmetic misbalance. To date the only depigmenting treatment for vitiligo approved by the FDA is the hydroquinone monobenzyl ether (monobenzone). We report the case of a patient with extensive vitiligo refractory to treatment managed with monobenzone. The result was successful for a long time, with partial relapse when the drug was discontinued. The relapse ended with the restart of the monobenzone. No new relapse seen with maintenance treatment 3 times a week. Monobenzone induces acromy due to melanocyte necrosis. To achieve depigmentation, it is used 1 to 2 times a day for 6 to 12 months. In adequately selected patients, it is a valid alternative for the management of vitiligo. A successful case of monobenzone depigmentation in dyschromia due to extensive vitiligo. Patient currently very satisfied with the results.

Pre-clinical evidences of Pyrostegia venusta in the treatment of vitiligo.

ETHNOPHARMACOLOGICAL RELEVANCE: Leaves of Pyrostegia venusta are popularly used to treat vitiligo; however, none in vivo study showed its ability. AIM OF THE STUDY: The overall objective of the present study was to evaluate the antiinflammatory and hyperpigmentant activities of hydroethanolic (HE) extract of leaves from P. venusta in animal models of vitiligo induced by croton oil and monobenzone. MATERIALS AND METHODS: The antiinflamatory and antioxidative effects of topical and oral administration of HE extract of P. venusta were evaluated in Swiss mice on edema model induced by croton oil, and further the N-acetyl-b-d-glucosaminidase (NAG) activity, cell infiltration, and cytokine and reactive species oxygen (ROS) levels. The involvement on mice pigmentation, cell infiltration and cytokine levels were evaluated on vitiligo model induced by monobenzone in C56BL/6 mice. RESULTS: HE of P. venusta by gavage (300 mg/kg) reduced NAG activity in 32.5 ± 5% on mouse ear edema induced by croton oil. Similarly, cell infiltration was lower (42.3 ± 5.9%) when compared to control group, as well as interleukin-1ß (IL-1ß), interleukin (IL-6) and tumor necrosis factor-α (TNF-α) levels, in 44.1 ± 9.7%, 71.9 ± 22.2% and to basal levels, respectively. Topical treatment with HE of P. venusta (10%) diminished cell infiltration (67.7 ± 7.1%) and ROS levels (total reduction). P. venusta either by gavage (300 mg/Kg) or topically (10%) increased epidermal melanin level (116.5 ± 13% and 100 ± 16.9%, respectively), diminished dermal depigmentation (36.0 ± 6.7% and 38.2 ± 6.2%, respectively), as well as tissue TNF-α levels (68.2 ± 11.6% and 99.2 ± 12.1%, respectively) and cell infiltration (basal levels and 94.3 ± 9.17%, respectively). However, only topical treatment with HE of P. venusta altered melanin specific marker in hair follicles. CONCLUSIONS: For the first time these data show that topical and oral administrations of P. venusta have significant antiinflammatory and hyperpigmentant effects, demonstrating different topical and systemic effects through two animal models. Together these models are capable to mimic several features founded in vitiligo, and the results support the ethnopharmacological use of P. venusta.

Comparison of topical application of tea polyphenol versus pimecrolimus versus tacrolimus for the treatment of monobenzone-induced vitiligo-like depigmentation in a mouse model / 中华皮肤科杂志

Objective To compare the therapeutic effect of topical application of tea polyphenol versus pimecrolimus versus tacrolimus for monobenzone-induced vitiligo-like depigmentation in mice.Methods Twentyfive 3-week-old female C57BL/6 mice were randomly and equally divided into 5 groups:negative control group,model group,tea polyphenol group,pimecrolimus group,tacrolimus group.Monobenzone 45％ cream was applied to the back of mice in all the five groups except the negative control group once daily for 40 consecutive days to establish a model of vitiligo-like depigmentation.During the induction of depigmentation,the tea polyphenol group,pimecrolimus group and tacrolimus group were topically treated with tea polyphenol,pimecrolimus and tacrolimus respectively,and the model group remaining untreated.The depigmentation of hairs and skin was observed by naked eyes on a daily basis.Tissue specimens were obtained for histological examination from depigmented skin at nonapplication sites in mice after the end of the experiment.Hematoxylin-eosin staining was conducted to analyze lymphocytic infiltration,reflectance confocal microscopy to observe melanin and melanocytes in skin,and immunofluorescence assay to detect CD8+ T cell infiltration.Results Depigmentation occurred in both application sites and non-application sites of mice in the model group.Compared with the model group,the tacrolimus,pimecrolimus and tea polyphenol groups showed delayed depigmentation,reduced degree and area index of depigmentation,and attenuated lymphocytic infiltration and CD8 + T cell infiltration in depigmented maculae at application sites.In addition,the therapeutic effect of tacrolimus was stronger than that of pimecrolimus and tea polyphenol.Conclusion Tea polyphenol,pimecrolimus and tacrolimus are all effective for the treatment of vitiligolike depigmentation in mice.

The therapeutic effects of EGCG on vitiligo.

Epigallocatechin-3-gallate (EGCG) is one of the main chemical constituents of green tea, which has been used as an important traditional Chinese medicine. Green tea has anti-inflammatory, anti-oxidant, and immunomodulatory properties. However, the effects of EGCG on vitiligo are not known. We assessed the role of EGCG in vitiligo induced by monobenzone in mice. We demonstrated that EGCG: delayed the time of depigmentation; reduced the prevalence of depigmentation; and decreased the area of depigmentation. Examination of depigmented skin treated with EGCG by reflectance confocal microscopy suggested increased numbers of epidermal melanocytes and histologic examination showed decreased perilesional accumulation of CD8(+) T cells. To further investigate the mechanism of the anti-inflammatory effects of EGCG, levels of inflammatory mediator tumor necrosis factor (TNF)-α, interferon (IFN)-γ and interleukin (IL)-6 were tested by enzyme-linked immunosorbent assay. Serum cytokine levels were significantly decreased after administration of EGCG compared with the model group. These results suggested that EGCG may have protective effects against vitiligo, and that it could contribute to suppression of activation of CD8(+) T cells and inflammatory mediators. Based on these results, 5% EGCG was considered to be the most suitable concentration for treating vitiligo, and was used for further study. In addition, we investigated the gene-expression profile of this model in relation to EGCG. Using a 4×44K whole genome oligo microarray assay, 1264 down-regulated genes and 1332 up-regulated genes were recorded in the 5% EGCG group compared with the model group, and selected genes were validated by real-time polymerase chain reaction. Our study demonstrated that EGCG administration was significantly associated with a decreased risk of vitiligo. EGCG could be a new preventive agent against vitiligo in the clinical setting.

Enhanced bleaching treatment: opportunities for immune-assisted melanocyte suicide in vitiligo.

Depigmentation in vitiligo occurs by progressive loss of melanocytes from the basal layer of the skin, and can be psychologically devastating to patients. T cell-mediated autoimmunity explains the progressive nature of this disease. Rather than being confronted with periods of rapid depigmentation and bouts of repigmentation, patients with long-standing, treatment-resistant vitiligo can undergo depigmentation treatment. The objective is to remove residual pigmentation to achieve a cosmetically acceptable result--that of skin with a uniform appearance. In the United States, only the use of mono-benzyl ether of hydroquinone (MBEH) is approved for this purpose. However, satisfactory results can take time to appear, and there is a risk of repigmentation. MBEH induces necrotic melanocyte death followed by a cytotoxic T-cell response to remaining, distant melanocytes. As cytotoxic T-cell responses are instrumental to depigmentation, we propose that combining MBEH with immune adjuvant therapies will accelerate immune-mediated melanocyte destruction to achieve faster, more definitive depigmentation than with MBEH alone. As Toll-like Receptor (TLR) agonists--imiquimod, CpG, and Heat Shock Protein 70 (HSP 70)--all support powerful Th1 responses, we propose that using MBEH in combination with these agents can achieve superior depigmentation results for vitiligo patients.

Effect of local acupuncture on monobenzone-induced vitiligo-like depigmentation in mice / 中华皮肤科杂志

Objective To evaluate the effect of injuries on monobenzone-induced vitiligo-like depigmentation in mice.Methods Forty C57BL/6 mice were randomly and equally divided into four groups:negative control group topically treated with vaseline cream,model group induced by topical monobenzone (40％) cream,acupuncture group receiving acupuncture treatment (15 times) once every three days,and acupuncture combined with monobenzone group receiving both monobenzone induction and acupuncture treatment.The treatment lasted 50 days and mice were sacrificed 15 days after the end of treatment.Hair decolorization was observed with naked eyes,and skin decolorization with reflectance confocal microscopy (RCM) on a daily basis.Tissue specimens were obtained from depigmented skin at monobenzone-uninduced sites,and subjected to hematoxylin and eosin (HE) staining for the cvaluation of lymphocytic infiltration as well as immunofluorescence staining for the detection of CD8+ T cell expression.Statistical analysis was done by t test.Results Varying degrees of depigmentation were observed in both monobenzone-induced and-uninduced sites in both the model group and acupuncture combined with monobenzone group,and the latter group showed earlier,larger and more stable depigmentation than the former group.At 15 days after the end of treatment,the decolorization area index in the model group and acupuncture combined with monobenzone group was 3.45 ± 0.17 and 3.90 ± 0.25 at monobenzone-induced sites respectively(t =7.433,P ＜ 0.05),1.90-± 0.12 and 2.85 ± 0.27 at monobenzone-uninduced sites respectively (t =7.529,P ＜ 0.05).Significant differences were observed in the fluorescence intensity of CD8 + T cells at monobenzone-uninduced depigmented sites between the model group and acupuncture combined with monobenzone group (175.528 ± 10.711 vs.645.928 ± 12.652,t =8.105,P ＜ 0.05),and there was a more evident infiltrate with lymphocytes and CD8+T cells in the monobenzone-uninduced depigmented sites in the acupuncture combined with monobenzone group.Conclusion Local destruction of skin barrier may promote monobenzone-induced vitiligo-like decolorization in mice.