Monobenzone-induced depigmentation: from enzymatic blockade to autoimmunity

The Effect of Monobenzone Cream on Oxidative Stress and Its Relationship With Serum Levels of IL-1β and IL-18 in Vitiligo Patients

BACKGROUND

Monobenzyl ether hydroquinone (MEBHQ) is a cream that promotes the spread and evenness of skin patches in vitiligo. Our aim was to investigate the oxidative and inflammatory effects of this cream on vitiligo patients consuming MEBHQ.

METHODS

A case-control study was conducted with three groups of 30 people from the control group, vitiligo patients before and after treatment. The percentage of vitiligo spots was determined by a specialist doctor. The levels of biochemical factors, oxidative stress profile and inflammatory factors were measured by enzymatic, colorimetric and ELISA methods, respectively.

RESULTS

Vitiligo patients showed a high level of inflammation and oxidative stress compared to healthy people. Although after 3 months of using MBEHQ cream, the percentage of skin spots in vitiligo patients increased from an average of 63%-91% and the skin color became almost uniform, but it still increased the level of oxidative stress and inflammation in these patients. Although the level of oxidative stress increased significantly in these patients, there was no significant increase in the level of malondialdehyde. The lack of significant differences in the levels of biochemical factors between healthy people and vitiligo patients before and after using the treatment shows the absence of side effects.

CONCLUSION

The use of MBEHQ increased the size of skin spots and uneven skin color in vitiligo patients. Although MBEHQ did not show side effects such as diabetes, liver and kidney diseases, it increased the levels of oxidative stress and inflammatory cytokines, which needs further study.

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.

Mechanisms of action of Lycium barbarum polysaccharide in protecting against vitiligo mice through modulation of the STAT3-Hsp70-CXCL9/CXCL10 pathway

CONTEXT

Vitiligo is a common skin disease with a complex pathogenesis, and so far, no effective treatment is available. Lycium barbarum L. (Solanaceae) polysaccharide (LBP), the main active ingredient of goji berries, has been demonstrated to protect keratinocytes and fibroblasts against oxidative stress.

OBJECTIVE

This study explored the effects and mechanism of LBP on monobenzone-induced vitiligo in mice.

MATERIALS AND METHODS

C57BL/6 mice were randomly divided into five groups (n = 6): negative control that received vaseline, vitiligo model group induced by monobenzone that treated with vaseline, positive control that received tacrolimus (TAC), LBP groups that received 0.3 and 0.6 g/kg LBP, respectively. We quantified the depigmentation by visual examination and scores, detected the expression of CD8+ T cells, pro-inflammatory cytokines and analysed the STAT3-Hsp70-CXCL9/CXCL10 pathway.

RESULTS

LBP 0.3 and 0.6 g/kg groups can significantly reduce depigmentation scores and the infiltration of local inflammatory cells in the skin lesions. Moreover, the expression of CXCL9, CXCL3, CXCL10 and HSP70 decreased by 54.3, 20.3, 48.5 and 27.2% in 0.3 g/kg LBP group, which decreased by 62.1, 26.6, 58.2 and 34.5% in 0.6 g/kg LBP group. In addition, 0.3 and 0.6 g/kg LBP decreased the release of IL-8 (9.7%, 22.8%), IL-6 (40.8%, 42.5%), TNF-α (25.7%, 35%), IFN-γ (25.1%, 27.6%) and IL-1β (23.7%, 33.7%) and inhibited the phosphorylation expression of STAT3 by 63.2 and 67.9%, respectively.

CONCLUSION

These findings indicated LBP might be recommended as a new approach for vitiligo which provide a theoretical basis for the clinical application of LBP in treating vitiligo patients.

A cell-based evaluation of human tyrosinase-mediated metabolic activation of leukoderma-inducing phenolic compounds

BACKGROUND

Chemical leukoderma is a skin depigmentation disorder induced through contact with certain chemicals, most of which have a p-substituted phenol structure similar to the melanin precursor tyrosine. The tyrosinase-catalyzed oxidation of phenols to highly reactive o-quinone metabolites is a critical step in inducing leukoderma through the production of melanocyte-specific damage and immunological responses.

OBJECTIVE

Our aim was to find an effective method to evaluate the formation of o-quinone by human tyrosinase and subsequent cellular reactions.

METHODS

Human tyrosinase-expressing 293T cells were exposed to various phenolic compounds, after which the reactive o-quinones generated were identified as adducts of cellular thiols. We further examined whether the o-quinone formation induces reductions in cellular GSH or viability.

RESULTS

Among the chemicals tested, all 7 leukoderma-inducing phenols/catechol (rhododendrol, raspberry ketone, monobenzone, 4-tert-butylphenol, 4-tert-butylcatechol, 4-S-cysteaminylphenol and p-cresol) were oxidized to o-quinone metabolites and were detected as adducts of cellular glutathione and cysteine, leading to cellular glutathione reduction, whereas 2-S-cysteaminylphenol and 4-n-butylresorcinol were not. In vitro analysis using a soluble variant of human tyrosinase revealed a similar substrate-specificity. Some leukoderma-inducing phenols exhibited tyrosinase-dependent cytotoxicity in this cell model and in B16BL6 melanoma cells where tyrosinase expression was effectively modulated by siRNA knockdown.

CONCLUSION

We developed a cell-based metabolite analytical method to detect human tyrosinase-catalyzed formation of o-quinone from phenolic compounds by analyzing their thiol-adducts. The detailed analysis of each metabolite was superior in sensitivity and specificity compared to cytotoxicity assays for detecting known leukoderma-inducing phenols, providing an effective strategy for safety evaluation of chemicals.

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.

A20 deficiency in myeloid cells deteriorates the onset of vitiligo in mice

Melanocyte-specific CD8⁺ T cells enrichment correlates with the severity of vitiligo, and the role of A20 derived from myeloid cells in the enrichment of pathogenic T cells is unknown. Premelanosome (PMEL)-specific transgenic CD8⁺ T cells were adoptive transferred into Krt14-Kitl* mice to construct the vitiligo model, which was further mated with A20^MKO mice and IKK2^fl/fl mice. Bone marrow cells were stimulated with 30% L929 cell-conditioned medium, Fc-human tumor necrosis factor, and lipopolysaccharides to induce bone marrow-derived macrophages (BMDMs). The relative expression of CCL2, CCL5, and IL12A was detected with real-time PCR, and nuclear factor kappa B (NFκB) related molecules were detected with Western blots. Fluorescence-activated cell sorting (FACS) was utilized to assay the percent of innate and adaptive immune cells in the spleen and bone marrow, and CD45⁺ T in the skin. Down-regulated A20 was detected in the skin biopsies of vitiligo patients. A20 deficiency did not affect the development of T cells, B cells, macrophages, and neutrophils. A20 negatively regulated the induction of proinflammatory chemokines (CCL2, CCL5, and IL12A) and NFκB-related molecule expression in BMDMs, which could be blocked by NFκB knockout. It further revealed that A20 negatively regulated the onset of vitiligo in mice with diminished CD45⁺ cells enrichment, which could also be reversed by NFκB knockout. A20 deficiency in myeloid cells could deteriorate the onset of vitiligo in mice, and A20 can be considered as a treatment target.

The Role of the NKG2D in Vitiligo

Vitiligo is an acquired multifactorial disease that affects melanocytes and results in skin depigmentation. In this review, we examine the role of cells stress and self-reactive T cells responses. Given the canonical and non-canonical functions of NKG2D, such as authenticating stressed target and enhance TCR signaling, we examine how melanocyte stress leads to the expression of ligands that are recognized by the activating receptor NKG2D, and how its signaling results in the turning of T cells against self (melanocyte suicide by proxy). We also discuss how this initiation phase is followed by T cell perpetuation, as NKG2D signaling results in self-sustained long-lasting T cells, with improved cytolytic properties.

Immune mediated mechanisms of melanocyte destruction: Paving the way for efficient immunotherapeutic strategies against melanoma

Insights into immune reactions against benign and malignant melanocytes may help the development of more efficient immunotherapeutic treatments for melanoma. The interplay between an active systemic antitumor immunity and a responsive local tumor environment is crucial to achieve effective clinical responses. Increasing evidence confirms this strategy can lead to an adequate and durable immunosurveillance of melanocytes.

Chemical induced pathognomonic features observed in human vitiligo are mediated through miR-2909 RNomics pathway

BACKGROUND

Chemicals like Monobenzyl Ether of Hydroquinone (MBEH) and 4-Tertiary Butyl Phenol (4-TBP) have been widely recognized to induce clinical lesions that resemble vitiligo, but exact molecular pathway through which these chemicals initiate vitiligo is still far from clear.

OBJECTIVES

Since vitiligo is widely considered as an autoimmune disease, this study was an attempt to understand miR-2909 RNomics in vitiligo pathogenesis using MBEH treated primary melanocytes as an archetype cellular model because MBEH causes pathological features indistinguishable from clinical vitiligo.

METHODS

Primary melanocytes were treated with MBEH and 4-TBP and the role of miR-2909 RNomics at transcriptional and translational level was explored through qRT-PCR, western blot analysis, flow cytometry, immunocytochemistry, immunohistochemistry and in silico binding affinities. 4 mm punch biopsies were also obtained from lesional sites of vitiligo patients to validate the results observed in cell culture experiments.

RESULTS

MBEH induced miR-2909 RNomics led to downregulation of MITF, TYR, TYRP1, and TYRP2 leading to decreased melanin synthesis which in turn is a characteristic trait of vitiligo. On the other hand, 4-TBP increased TGF-β which also has the intrinsic capacity to downregulate MITF leading to decreased melanin synthesis and thereby initiation of vitiligo.

CONCLUSION

Based upon our results we propose a molecular pathway which has the inherent capacity to resolve the mechanism through which these chemicals may induce vitiligo. This mechanism was also found to be involved in the lesional biopsies of vitiligo patients. These results could be exploited in better understanding the pathogenesis as well as in treatment of vitiligo.

Mechanism of action of 4-substituted phenols to induce vitiligo and antimelanoma immunity

Monobenzone is a 4-substituted phenol that can induce vitiligo and antimelanoma immunity. We investigated the influence of the chemical structure on the biological activity of a series of structurally related 4-substituted phenols. All phenols inhibited cellular melanin synthesis, and eight of ten phenols inhibited tyrosinase activity, using the MBTH assay. These phenols also induced glutathione (GSH) depletion, indicative of quinone formation and protein thiol binding, which can increase the immunogenicity of melanosomal proteins. Specific T-cell activation was found upon stimulation with phenol-exposed pigmented cells, which also reacted with unexposed cells. In contrast, 4-tertbutylphenol induced immune activation was not restricted to pigment cells, analogous to contact sensitization. We conclude that 4-substituted phenols can induce specific T-cell responses against melanocytes and melanoma cells, also acting at distant, unexposed body sites, and may confer a risk of chemical vitiligo. Conversely, these phenols may be applicable to induce specific antimelanoma immunity.

The Evaluation of Vitiligous lesions Repigmentation after the Administration of Atorvastatin calcium salt and Simvastatin-acid sodium salt in patients with active vitiligo (EVRAAS), a pilot study: study protocol for a randomized controlled trial

Background

Vitiligo is a chronic skin disorder presenting with depigmentation, the pathogenesis of which is complex but the autoimmune theory is now preferred. Multiple immunologic processes, including stimulation of the T-helper (Th)1 response, formation of autoreactive melanocyte-specific CD8⁺ T lymphocytes, a decrease in the blood concentration of T regulatory (Treg) cells, and an increase in interleukin (IL)-17 and interferon (IFN) concentration, have been shown to contribute to vitiligo progression and maintenance. The aim of this study is to evaluate the influence of simvastatin and atorvastatin on vitiligous lesions in patients with nonsegmental vitiligo (NSV). According to available data, statins act through several immunological pathways, potentially reversing undesirable phenomena underlying autoimmune vitiligo pathogenesis.

Methods/design

A study has been designed as a single-center, randomized, double-blind, placebo-controlled pilot study with the enrollment of at least 24 active NSV patients presenting with vitiligous lesions on both upper and lower limbs. The clinical effects of ointments containing 1% simvastatin-acid sodium salt or 1% atorvastatin calcium salt applied on a preselected limb will be assessed in comparison with vehicle ointment applied on the opposite limb. All study participants will undergo clinical evaluation using body surface area (BSA) and Vitiligo Area Scoring Index (VASI) scales at baseline and at weeks 4, 8, and 12 time points. A precise assessment of skin lesions will be performed using photographic documentation obtained during each study visit and processed with NIS-Elements software.

Discussion

Currently available vitiligo topical therapeutic approaches including calcineurin inhibitors and corticosteroids remain poorly effective and are associated with either relatively high cost or potentially dangerous adverse effects. The clinical application of orally administrated statins, widely used as systemic cholesterol-lowering agents, in vitiligous patients has only been tested in two clinical trials; however, data on their potential usefulness is scarce. Moreover, due to a high risk of clinically significant toxicity, topical administration was recommended by researchers. This study is the first to evaluate safety and efficacy of the topical use of statins in patients presenting with NSV.

Trial registration

Clinicaltrials.gov, NCT03247400. Registered on 05 August 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-3168-4) contains supplementary material, which is available to authorized users.

Flavonoids as adjuvant in psoralen based photochemotherapy in the management of vitiligo/leucoderma

Vitiligo is a disorder characterized by the decrease in melanin pigment of skin. This depigmenting disorder has prevalence among worldwide, irrespective of age and sex. There is an existence of different treatment modalities for the management of vitiligo. But irrespective of treatment methods, the main drawback in the management of vitiligo is the occurrence of side effects during the implication of treatment. Among the treatment modalities, photochemotherapy seems to be the better choice of treatment for vitiligo. Photochemotherapy involves the usage of UV rays for photoactivation of the drug to cause photosensitization of skin which in turn leads to repigmentation. The main aim of the study is to develop novel combination strategy of lipid based nanoemulsion gel for the treatment of leucoderma using trimethylpsoralen and flavonoid. We assume that if this hypothesis of combination therapy proves successful it can be used as an additional novel treatment strategy in the management of vitiligo.

Mouse Model for Human Vitiligo

Vitiligo is an autoimmune skin disease in which the pigment-producing melanocytes are destroyed by autoreactive CD8⁺ T cells. As a result, patients develop disfiguring white spots on the skin. This article discusses the first mouse model of vitiligo that develops epidermal depigmentation, similar to disease in human patients. To achieve epidermal depigmentation, mice are genetically engineered to retain melanocytes in the skin epidermis. Induction of disease occurs by adoptive transfer of melanocyte-specific CD8⁺ T cells into recipient mice and the subsequent activation of these T cells using a viral vector. Depigmentation of the epidermis occurs within 5 to 7 weeks in a patchy pattern similar to patients with vitiligo. This article describes the methods of vitiligo induction, quantification of lesion progression and regression, processing of the skin for detailed analysis, and how to use this model to inform clinical studies. © 2018 by John Wiley & Sons, Inc.

The convergence theory for vitiligo: A reappraisal

Vitiligo is characterized by progressive loss of skin pigmentation. The search for aetiologic factors has led to the biochemical, the neurologic and the autoimmune theory. The convergence theory was then proposed several years ago to incorporate existing theories of vitiligo development into a single overview of vitiligo aetiology. The viewpoint that vitiligo is not caused only by predisposing mutations, or only by melanocytes responding to chemical/radiation exposure, or only by hyperreactive T cells, but rather results from a combination of aetiologic factors that impact melanocyte viability, has certainly stood the test of time. New findings have since informed the description of progressive depigmentation. Understanding the relative importance of such aetiologic factors combined with a careful selection of the most targetable pathways will continue to drive the next phase in vitiligo research: the development of effective therapeutics. In that arena, it is likewise important to acknowledge that pathways affected in some patients may not be altered in others. Taken together, the convergence theory continues to provide a comprehensive viewpoint of vitiligo aetiology. The theory serves to intertwine aetiologic pathways and will help to define pathways amenable to disease intervention in individual patients.

The nuclear factor (erythroid-derived 2)-like 2 (NRF2) antioxidant response promotes melanocyte viability and reduces toxicity of the vitiligo-inducing phenol monobenzone

Vitiligo, characterised by progressive melanocyte death, can be initiated by exposure to vitiligo-inducing phenols (VIPs). VIPs generate oxidative stress in melanocytes and activate the master antioxidant regulator NRF2. While NRF2-regulated antioxidants are reported to protect melanocytes from oxidative stress, the role of NRF2 in the melanocyte response to monobenzone, a clinically relevant VIP, has not been characterised. We hypothesised that activation of NRF2 may protect melanocytes from monobenzone-induced toxicity. We observed that knockdown of NRF2 or NRF2-regulated antioxidants NQO1 and PRDX6 reduced melanocyte viability, but not viability of keratinocytes and fibroblasts, suggesting that melanocytes were preferentially dependent upon NRF2 activity for growth compared to other cutaneous cells. Furthermore, melanocytes activated the NRF2 response following monobenzone exposure and constitutive NRF2 activation reduced monobenzone toxicity, supporting NRF2's role in the melanocyte stress response. In contrast, melanocytes from individuals with vitiligo (vitiligo melanocytes) did not activate the NRF2 response as efficiently. Dimethyl fumarate-mediated NRF2 activation protected normal and vitiligo melanocytes against monobenzone-induced toxicity. Given the contribution of oxidant-antioxidant imbalance in vitiligo, modulation of this pathway may be of therapeutic interest.

Anti-Melanoma immunity and local regression of cutaneous metastases in melanoma patients treated with monobenzone and imiquimod; a phase 2 a trial

Vitiligo development in melanoma patients during immunotherapy is a favorable prognostic sign and indicates breakage of tolerance against melanocytic/melanoma antigens. We investigated a novel immunotherapeutic approach of the skin-depigmenting compound monobenzone synergizing with imiquimod in inducing antimelanoma immunity and melanoma regression. Stage III-IV melanoma patients with non-resectable cutaneous melanoma metastases were treated with monobenzone and imiquimod (MI) therapy applied locally to cutaneous metastases and adjacent skin during 12 weeks, or longer. Twenty-one of 25 enrolled patients were evaluable for clinical assessment at 12 weeks. MI therapy was well-tolerated. Partial regression of cutaneous metastases was observed in 8 patients and stable disease in 1 patient, reaching the statistical endpoint of treatment efficacy. Continued treatment induced clinical response in 11 patients, including complete responses in three patients. Seven patients developed vitiligo-like depigmentation on areas of skin that were not treated with MI therapy, indicating a systemic effect of MI therapy. Melanoma-specific antibody responses were induced in 7 of 17 patients tested and melanoma-specific CD8+T-cell responses in 11 of 15 patients tested. These systemic immune responses were significantly increased during therapy as compared to baseline in responding patients. This study shows that MI therapy induces local and systemic anti-melanoma immunity and local regression of cutaneous metastases in 38% of patients, or 52% during prolonged therapy. This study provides proof-of-concept of MI therapy, a low-cost, broadly applicable and well-tolerated treatment for cutaneous melanoma metastases, attractive for further clinical investigation.

Inflammasome-Dependent Induction of Adaptive NK Cell Memory

Monobenzone is a pro-hapten that is exclusively metabolized by melanocytes, thereby haptenizing melanocyte-specific antigens, which results in cytotoxic autoimmunity specifically against pigmented cells. Studying monobenzone in a setting of contact hypersensitivity (CHS), we observed that monobenzone induced a long-lasting, melanocyte-specific immune response that was dependent on NK cells, yet fully intact in the absence of T- and B cells. Consistent with the concept of "memory NK cells," monobenzone-induced NK cells resided in the liver and transfer of these cells conferred melanocyte-specific immunity to naive animals. Monobenzone-exposed skin displayed macrophage infiltration and cutaneous lymph nodes showed an inflammasome-dependent influx of macrophages with a tissue-resident phenotype, coinciding with local NK cell activation. Indeed, macrophage depletion or the absence of the NLRP3 inflammasome, the adaptor protein ASC or interleukin-18 (IL-18) abolished monobenzone CHS, thereby establishing a non-redundant role for the NLRP3 inflammasome as a critical proinflammatory checkpoint in the induction of hapten-dependent memory NK cells.

Vitiligo: How do oxidative stress-induced autoantigens trigger autoimmunity?

Vitiligo is a common depigmentation disorder characterized by a loss of functional melanocytes and melanin from epidermis, in which the autoantigens and subsequent autoimmunity caused by oxidative stress play significant roles according to hypotheses. Various factors lead to reactive oxygen species (ROS) overproduction in the melanocytes of vitiligo: the exogenous and endogenous stimuli that cause ROS production, low levels of enzymatic and non-enzymatic antioxidants, disturbed antioxidant pathways and polymorphisms of ROS-associated genes. These factors synergistically contribute to the accumulation of ROS in melanocytes, finally leading to melanocyte damage and the production of autoantigens through the following ways: apoptosis, accumulation of misfolded peptides and cytokines induced by endoplasmic reticulum stress as well as the sustained unfolded protein response, and an 'eat me' signal for phagocytic cells triggered by calreticulin. Subsequently, autoantigens presentation and dendritic cells maturation occurred mediated by the release of antigen-containing exosomes, adenosine triphosphate and melanosomal autophagy. With the involvement of inducible heat shock protein 70, cellular immunity targeting autoantigens takes the essential place in the destruction of melanocytes, which eventually results in vitiligo. Several treatments, such as narrow band ultraviolet, quercetin and α-melanophore-stimulating hormone, are reported to be able to lower ROS thereby achieving repigmentation in vitiligo. In therapies targeting autoimmunity, restore of regulatory T cells is absorbing attention, in which narrow band ultraviolet also plays a role.

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-1β (IL-1β), 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.

Simvastatin prevents and reverses depigmentation in a mouse model of vitiligo

Vitiligo is a common autoimmune disease of the skin that results in disfiguring white spots. There are no FDA-approved treatments, and current treatments are time-consuming, expensive, and have low efficacy. We sought to identify new treatments for vitiligo, and first considered repurposed medications because of the availability of safety data and expedited regulatory approval. We previously reported that the IFN-γ-induced chemokine CXCL10 is expressed in lesional skin from vitiligo patients, and that it is critical for the progression and maintenance of depigmentation in our mouse model of vitiligo. We hypothesized that targeting IFN-γ signaling might be an effective new treatment strategy. STAT1 activation is required for IFN-γ signaling and recent studies revealed that simvastatin, an FDA-approved cholesterol-lowering medication, inhibited STAT1 activation in vitro. Therefore, we hypothesized that simvastatin may be an effective treatment for vitiligo. We found that simvastatin both prevented and reversed depigmentation in our mouse model of vitiligo, and reduced the number of infiltrating autoreactive CD8⁺ T cells in the skin. Treatment of melanocyte-specific, CD8⁺ T cells in vitro decreased proliferation and IFN-γ production, suggesting additional effects of simvastatin directly on T cells. Based on these data, simvastatin may be a safe, targeted treatment option for patients with vitiligo.

CXCL10 is critical for the progression and maintenance of depigmentation in a mouse model of vitiligo

Vitiligo is an autoimmune disease of the skin that results in disfiguring white spots. There are no U.S. Food and Drug Administration-approved treatments for vitiligo, and most off-label treatments yield unsatisfactory results. Vitiligo patients have increased numbers of autoreactive, melanocyte-specific CD8(+) T cells in the skin and blood, which are directly responsible for melanocyte destruction. We report that gene expression in lesional skin from vitiligo patients revealed an interferon-γ (IFN-γ)-specific signature, including the chemokine CXCL10. CXCL10 was elevated in both vitiligo patient skin and serum, and CXCR3, its receptor, was expressed on pathogenic T cells. To address the function of CXCL10 in vitiligo, we used a mouse model of disease that also exhibited an IFN-γ-specific gene signature, expression of CXCL10 in the skin, and up-regulation of CXCR3 on antigen-specific T cells. Mice that received Cxcr3(-/-) T cells developed minimal depigmentation, as did mice lacking Cxcl10 or treated with CXCL10-neutralizing antibody. CXCL9 promoted autoreactive T cell global recruitment to the skin but not effector function, whereas CXCL10 was required for effector function and localization within the skin. Surprisingly, CXCL10 neutralization in mice with established, widespread depigmentation induces reversal of disease, evidenced by repigmentation. These data identify a critical role for CXCL10 in both the progression and maintenance of vitiligo and thereby support inhibiting CXCL10 as a targeted treatment strategy.

A mouse model of vitiligo induced by monobenzone

The paucity of vitiligo animal models limits the understanding of vitiligo pathogenesis and the development of therapies for the skin disorder. In this study, we developed a new mouse model of vitiligo by topically applying the skin-depigmenting agent monobenzone on mice. We demonstrated that monobenzone-induced skin depigmentation on the non-exposed sites and that the severity of lesions depended on drug dosage. The result of the histological examination of the depigmented skin indicated loss of epidermal melanocytes and perilesional accumulation of CD8⁺ T cells. Furthermore, the monobenzone-induced depigmentation of the Rag1 gene knockout did not appear on the non-exposed sites, supporting the involvement of infiltrating CD8⁺ T cells in melanocyte destruction. Resemblance in histological characteristics and pathogenesis between monobenzone-induced depigmentation and active human vitiligo suggests good potential of our mouse model for use in vitiligo research.

Depigmentation Therapy with Q-Switched Nd: YAG Laser in Universal Vitiligo

Background:

Any residual pigment left in patients of universal vitiligo is managed with topical treatments, cryotherapy, and lasers.

Aim:

The study aims to assess the efficacy and safety of Q-switched Nd: YAG laser in treating the residual pigmentation in patients with universal vitiligo.

Materials and Methods:

Fifteen patients of universal vitiligo with residual pigmentation on the face, hands, or feet, resistant to topical treatments, were treated with single or multiple sessions of Q-switched Nd: YAG laser treatment. Topical treatments were continued in between the laser sessions and the depigmentation achieved was monitored by clinical examination and repeat digital photographs. Response to the treatment was labelled as excellent if the residual pigment could be reduced by at least 90% while 50–90% resolution of pigmentation was labelled as a partial response. Adverse effects to the treatment offered were also monitored.

Results:

Thirteen of the 15 patients enrolled for the study showed an excellent response to the treatment offered. Two other patients showed a poor response with less than 50% resolution of pigmentation. The number of laser sessions needed at a particular site ranged from 1 to 3 and no patient was offered more than three sessions of laser treatment at any site. No significant adverse events were reported by any patient.

Conclusions:

Residual pigmentation in patients with universal vitiligo that does not respond to topical treatment options alone can be managed quite effectively with Q-switched Nd: YAG laser without any significant adverse effects.

Melanoma-Targeted Chemothermotherapy and In Situ Peptide Immunotherapy through HSP Production by Using Melanogenesis Substrate, NPrCAP, and Magnetite Nanoparticles

Exploitation of biological properties unique to cancer cells may provide a novel approach to overcome difficult challenges to the treatment of advanced melanoma. In order to develop melanoma-targeted chemothermoimmunotherapy, a melanogenesis substrate, N-propionyl-4-S-cysteaminylphenol (NPrCAP), sulfur-amine analogue of tyrosine, was conjugated with magnetite nanoparticles. NPrCAP was exploited from melanogenesis substrates, which are expected to be selectively incorporated into melanoma cells and produce highly reactive free radicals through reacting with tyrosinase, resulting in chemotherapeutic and immunotherapeutic effects by oxidative stress and apoptotic cell death. Magnetite nanoparticles were conjugated with NPrCAP to introduce thermotherapeutic and immunotherapeutic effects through nonapoptotic cell death and generation of heat shock protein (HSP) upon exposure to alternating magnetic field (AMF). During these therapeutic processes, NPrCAP was also expected to provide melanoma-targeted drug delivery system.

Vitiligo: an update on current pharmacotherapy and future directions

INTRODUCTION

Vitiligo is a common pigmentary skin disorder, characterized by the appearance of white macules on the skin, mucosal or hair. Treatment is often a tough challenge and involves a wide range of therapies.

AREAS COVERED

This review focuses on available first- and second-line pharmacological treatments for vitiligo. In particular, the mechanisms of action, the main indications, the efficacy and the most important side effects are reviewed. Moreover, a brief discussion is provided, regarding other nonpharmacological treatments, such as phototherapy and surgical options, due to their importance and successful outcomes in vitiligo treatment. Finally, a concise overview regarding the future directions in vitiligo therapy is presented.

EXPERT OPINION

The promising outcomes reported here demonstrate that it is possible to achieve a satisfactory and often stable repigmentation of vitiligo lesions. Topical corticosteroids, calcineurin inhibitors, phototherapy and photochemotherapy represent the first-line therapeutic options, due to their safety and efficacy, whereas vitamin D analogues, targeted phototherapy, oral corticosteroids and surgery should be used as second-line therapies. Other therapies, such as antioxidants, can be used in association with other therapeutic options, whereas depigmenting agents should be used only in cases of extensive vitiligo, recalcitrant to other treatments.

The gluttonous side of malignant melanoma: basic and clinical implications of macroautophagy

True to their inherent aggressive behavior, melanomas keep impressing the melanoma community with their ability to bypass tumor suppressor mechanisms. Name a pathway with the potential to control cell survival and melanoma cells will likely have it potentiated by multiple genetic or epigenetic alterations. In the context of progression and chemoresistance, large efforts have been dedicated to the identification of protective mechanisms associated with or linked to apoptotic death programs. These studies have guided the design of targeted anticancer strategies. Still, the promise for pro-apoptotic inducers as lead compounds for drug development has yet to come to fruition. It was then a question of time to identify alternative modulators of cell viability. An ideal candidate that is raising great expectations in the oncology field is autophagy, a catabolic process with multiple roles in cell homeostasis. Here we review the incipient literature on autophagy markers in melanocytic lesions. Intriguingly, histopathological studies are unveiling an intrinsic inter- and intratumor variability in the expression of autophagy modulators. Nonetheless, functional studies support a key role of autopaphagy programs in the response to a variety of stress factors. These include adaptive responses to nutrient deprivation, hypoxia and many anticancer agents, among other stimuli. Strategies are being also developed to mobilize the endocytic machinery and shift autolysosomes into death effectors. The opportunities that lie ahead in this field are exciting. Various authophagy mediators are potentially druggable. Moreover, animal models and the development of sophisticated screening methods offer a platform for multilevel academic-industrial collaborations. These efforts are expected to open avenues of research and, hopefully, lead to a more rational approach to melanoma treatment.