Why treatments do(n't) work in vitiligo: An autoinflammatory perspective

Treatment update for vitiligo based on autoimmune inhibition and melanocyte protection

INTRODUCTION

The treatment of vitiligo remains challenging due to the complexity of its pathogenesis, influenced by genetic factors, oxidative stress and abnormal cell adhesion that collectively impact melanocyte survival and trigger immune system attacks, resulting in melanocyte death. Melanocytes in vitiligo are believed to exhibit genetic susceptibility and defects in cellular mechanisms, such as defects in autophagy, that reduce their ability to resist oxidative stress, leading to increased expression of the pro-inflammatory protein HSP70. The low expression of adhesion molecules, such as DDR1 and E-cadherin, accelerates melanocyte damage and antigen exposure. Consequently, autoimmune attacks centered on IFN-γ-CXCR9/10-CXCR3-CD8⁺ T cells are initiated, causing vitiligo.

AREAS COVERED

This review discusses the latest knowledge on the pathogenesis of vitiligo and potential therapeutic targets from the perspective of suppressing autoimmune attacks and activating melanocytes functions.

EXPERT OPINION

Vitiligo is one of the most challenging dermatological diseases due to its complex pathogenesis with diverse therapeutic targets. Immune suppression, such as corticosteroids and emerging JAK inhibitors, has proven effective in disease progression. However, during the early stages of the disease, it is also important to optimize therapeutic strategies to activate melanocytes for alleviating oxidative stress and improving treatment outcomes.

Where Microneedle Meets Biomarkers: Futuristic Application for Diagnosing and Monitoring Localized External Organ Diseases

Extracellular tissue fluids are interesting biomatrices that have recently attracted scientists' interest. Many significant biomarkers for localized external organ diseases have been isolated from this biofluid. In the diagnostic and disease monitoring context, measuring biochemical entities from the fluids surrounding the diseased tissues may give more important clinical value than measuring them at a systemic level. Despite all these facts, pushing tissue fluid-based diagnosis and monitoring forward to clinical settings faces one major problem: its accessibility. Most extracellular tissue fluid, such as interstitial fluid (ISF), is abundant but hard to collect, and the currently available technologies are invasive and expensive. This is where novel microneedle technology can help tackle this significant obstacle. The ability of microneedle technology to minimally invasively access tissue fluid-containing biomarkers will enable ISF and other tissue fluid utilization in the clinical diagnosis and monitoring of localized diseases. This review attempts to present the current pursuit of the application of microneedle systems as a diagnostic and monitoring platform, along with the recent progress of biomarker detection in diagnosing and monitoring localized external organ diseases. Then, the potential use of various microneedles in future clinical diagnostics and monitoring of localized diseases is discussed by presenting the currently studied cases.

The role of cytokines and vitamin D in vitiligo pathogenesis

Vitiligo is a pigment-related disease with a global prevalence of 0.2% to 1.8% associated with considerable burden on quality of life. The treatment is still a challenge because of relapses and/or incomplete re-pigmentation. Although the exact cause is still unclear, its pathogenesis seems to be justifiable with the autoimmune theory, supported by the results of clinical research. In this narrative review, we aimed to summarize the evidence related to cytokines and vitiligo development. This review is consisted of English articles published in PubMed and Google Scholar concerning levels of inflammatory mediators, especially interleukins, in vitiligo patients over the last 20 years. References of relevant articles were also considered for review. Crucial role of dysregulated levels of interleukins and their synergistic function to each other, in the onset or progression of the disease is evident. The theory of autoimmune vitiligo is reinforced by the results of the studies in the literature, due to the association of pathogenesis with increased secretion of pro-inflammatory mediators and reduction of anti-inflammatory mediators. Decreased vitamin D levels may have a considerable role in vitiligo development by affecting Th1- and Th17-related immune responses. Cytokines play an important role in the pathogenesis or progression of the disease. Moreover, we believe that decreased vitamin D level has a considerable role in vitiligo development by affecting Th1- and Th17-related immune responses.

Presence and the roles of IL-9/Th9 axis in vitiligo

Immune dysregulation is critical in vitiligo pathogenesis. Although the presence and roles of numerous CD4⁺ T-cell subsets have been described, the presence of Th9 cells and more importantly, roles of IL-9 on melanocyte functions are not explored yet. Here, we quantified the T helper cell subsets including Th9 cells in vitiligo patients by multicolor flowcytometry. There was an increased frequency of skin-homing (CLA⁺ ) and systemic (CLA^- ) Th9 cells in vitiligo patients compared to healthy donors. However, there was no difference in Th9 cell frequency in vitiligo patients with early and chronic disease. There was negligible IL-9 receptor (IL-9R) expression on human primary melanocytes (HPMs); however, IFNγ upregulated IL-9R expression on HPMs. Functionally, IL-9/IL-9R signaling reduced the production of IFNγ-induced toxic reactive oxygen species (ROS) in HPMs. There was no effect of IL-9 on expression of genes responsible for melanosome formation (MART1, TYRP1, and DCT), melanin synthesis (TYR), and melanocyte-inducing transcription factor (MITF) in HPMs. In conclusion, this study identifies the presence of Th9 cells in vitiligo and their roles in reducing the oxidative stress of melanocytes, which might be useful in designing effective therapeutics.

NB-UVB plus oral Polypodium leucotomos extract display higher efficacy than NB-UVB alone in patients with vitiligo

Polypodium leucotomos displayed a synergic effect with NB-UVB in psoriasis, but its application on vitiligo remains understudied. The aim of this study was to investigate whether oral supplementation with leaves extract of Polypodium leucotomos (PL) improves narrow band (NB) UVB phototherapy-induced repigmentation. Forty-four patients with generalized vitiligo were enrolled in this randomized, prospective, placebo controlled study. Twenty-three patients were randomly selected to receive combined treatment with NB-UVB phototherapy and 480 mg oral PL twice daily while 21 patients received NB-UVB phototherapy combined with placebo. All subjects were treated with NB-UVB twice weekly for 6 months. Our results demonstrated that oral PL combined with NB-UVB improved repigmentation as well as increased the response rate compared with patients treated with NB-UVB alone (47.8% vs 22%). Our study suggests that oral supplementation of PL and NB-UVB phototherapy enhance the extent of repigmentation.

Vitiligo: A Review

Vitiligo, a common depigmenting skin disorder, has an estimated prevalence of 0.5–2% of the population worldwide. The disease is characterized by the selective loss of melanocytes which results in typical nonscaly, chalky-white macules. In recent years, considerable progress has been made in our understanding of the pathogenesis of vitiligo which is now clearly classified as an autoimmune disease. Vitiligo is often dismissed as a cosmetic problem, although its effects can be psychologically devastating, often with a considerable burden on daily life. In 2011, an international consensus classified segmental vitiligo separately from all other forms of vitiligo, and the term vitiligo was defined to designate all forms of nonsegmental vitiligo. This review summarizes the current knowledge on vitiligo and attempts to give an overview of the future in vitiligo treatment.

Premature cell senescence in human skin: Dual face in chronic acquired pigmentary disorders

Although senescence was originally described as an in vitro acquired cellular characteristic, it was recently recognized that senescence is physiologically and pathologically involved in aging and age-related diseases in vivo. The definition of cellular senescence has expanded to include the growth arrest caused by various cellular stresses, including DNA damage, inadequate mitochondria function, activated oncogene or tumor suppressor genes and oxidative stress. While senescence in normal aging involves various tissues over time and contributes to a decline in tissue function even with healthy aging, disease-induced premature senescence may be restricted to one or a few organs triggering a prolonged and more intense rate of accumulation of senescent cells than in normal aging. Organ-specific high senescence rate could lead to chronic diseases, especially in post-mitotic rich tissue. Recently, two opposite acquired pathological conditions related to skin pigmentation were described to be associated with premature senescence: vitiligo and melasma. In both cases, it was demonstrated that pathological dysfunctions are not restricted to melanocytes, the cell type responsible for melanin production and transport to surrounding keratinocytes. Similar to physiological melanogenesis, dermal and epidermal cells contribute directly and indirectly to deregulate skin pigmentation as a result of complex intercellular communication. Thus, despite senescence usually being reported as a uniform phenotype sharing the expression of characteristic markers, skin senescence involving mainly the dermal compartment and its paracrine function could be associated with the disappearance of melanocytes in vitiligo lesions and with the exacerbated activity of melanocytes in the hyperpigmentation spots of melasma. This suggests that the difference may arise in melanocyte intrinsic differences and/or in highly defined microenvironment peculiarities poorly explored at the current state of the art. A similar dualistic phenotype has been attributed to intratumoral stromal cells as cancer-associated fibroblasts presenting a senescent-like phenotype which influence the behavior of neoplastic cells in either a tumor-promoting or tumor-inhibiting manner. Here, we present a framework dissecting senescent-related molecular alterations shared by vitiligo and melasma patients and we also discuss disease-specific differences representing new challenges for treatment.

Identification of pathogenic genes and transcription factors in vitiligo

Our study aimed to identify the key genes and upstream regulators in vitiligo. To screen the pathogenic genes of vitiligo, an integrated analysis was performed by using the microarray datasets in vitiligo derived from the Gene Expression Omnibus (GEO) database. The functional annotation and potential pathways of differentially expressed genes (DEGs) were further explored by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. We constructed a vitiligo-specific transcriptional regulatory network to identify crucial transcriptional factors that target the DEGs in vitiligo. From two GEO datasets, we identified 1863 DEGs (744 downregulated DEGs and 1,119 upregulated DEGs [false discovery rate < 0.05, |Combined.ES| > 1]) between lesional tissues and nonlesional tissues. GO and KEGG analyses revealed that ubiquitin-mediated proteolysis and the endoplasmic reticulum were significantly enriched pathways for DEGs. The expressions of premelanosome (PMEL), melan-A (MLANA), dopachrome tautomerase (DCT), SRY-boxtranscription factor 10 (SOX10), tyrosinase-related protein 1 (TYRP1), and melanocortin 1 receptor (MC1R) were shown to be involved in the pathogenesis of vitiligo. We concluded that PMEL, MLANA), DCT, SOX10, TYRP1, and MC1R may play a role in vitiligo, among which TYRP1 and MC1R are regulated by forkhead box J2 (FOXJ2). Our finding may contribute to the development of new potential biomarkers, reveal the underlying pathogenesis of vitiligo, and identify novel therapeutic targets for vitiligo.

Amine derivatives of furocoumarin induce melanogenesis by activating Akt/GSK-3β/β-catenin signal pathway

Background

Melanogenesis, or the biosynthesis of melanin, plays a critical role in the pigmentation of skin, hair, and eyes. Reduced melanogenesis may lead to depigmentation conditions such as vitiligo. Psoralen, a furocoumarin derivative, is closely associated with melanogenesis, and its derivative 8-methoxypsoralen is used in psoralen and ultraviolet A therapy for pigmentation disorders. In a previous study, we synthesized a new series of amine derivatives of furocoumarin, of which 5-(morpholinomethyl)-3-phenyl-7H-furo[3,2-g]chromen-7-one (encoded as D206008) showed a remarkable melanogenic effect in B16 murine cells.

Methods

In this study, we examined the effects of D206008 on the melanogenesis-related pathways in B16 cells. D206008 increased melanin production and tyrosinase (TYR) activity, as well as the mRNA and protein expression levels of the melanogenic enzymes TYR, TRP-1 and TRP-2, and the melanogenesis-related transcription factor microphthalmia-associated transcription factor (MITF) in a dose-dependent (0–100 µM) and time-dependent (0–48 hours) manner.

Results

Mechanistically, D206008 inhibited β-catenin degradation by enhancing the phosphorylation of Akt and glycogen synthase kinase-3β (GSK-3β), which increased the accumulation of β-catenin in the cytoplasm. Nuclear translocation of β-catenin also increased in response to D206008 treatment.

Conclusion

Taken together, these data indicate that D206008 promotes melanin synthesis by stimulating the nuclear translocation of β-catenin, which activates MITF transcription and eventually melanogenesis.

Vitamin D protects human melanocytes against oxidative damage by activation of Wnt/β-catenin signaling

Vitamin D analogs have been widely utilized for the treatment of vitiligo, but the molecular mechanism underlying their pharmacological effects (especially their antioxidant properties) has not yet been investigated. We evaluated the relationship between serum vitamin D level and oxidative damage severity in vitiligo patients, and investigated the molecular mechanism of vitamin D in protecting melanocytes against oxidative stress. Serum levels of 25-hydroxyvitamin D and malondialdehyde (MDA) were first measured in patients. A variety of in vitro experiments such as intracellular reactive oxygen species (ROS), cellular viability, migration, and apoptotic assays were then performed to detect the effects of vitamin D or β-catenin silencing on H₂O₂-treated melanocytes. Expression of Wnt/β-catenin, Nrf2, apoptotic, and MITF pathways was finally examined using quantitative real-time PCR and western blot. In this study, we initially found that vitamin D insufficiency was closely associated with the severity of oxidative stress in vitiligo patients. Using ex vivo cell models, we further showed that vitamin D positively modulated β-catenin signaling at both translational and posttranslational levels in melanocytes under oxidative stress. Like WNT agonists, vitamin D significantly inhibited ROS accumulation and cell apoptosis in H₂O₂-treated melanocytes and promoted their proliferative and migratory activity, while the protective effects of vitamin D against oxidative stress were abolished by β-catenin silencing in melanocytes. Furthermore, β-catenin deficiency also blocked the activation of Nrf2 and MITF as well as the inhibition of apoptosis induced by vitamin D. Taken together, vitamin D insufficiency was associated with severity of oxidative stress in vitiligo patients. Our work also provides new insights into the mechanism of vitamin D against vitiligo, in which vitamin D protects melanocytes against oxidative stress by activating Wnt/β-catenin signaling.

The role of interleukins in vitiligo: a systematic review

Vitiligo is a disorder of the skin that causes depigmentation and asymptomatic macules whose exact cause is still unclear. Although its aetiology is not fully elucidated, the main theory of its pathomechanism is that it is associated with the autoimmune process. There is few summarized information about the role of inflammatory mediators, as interleukins, in vitiligo, so our aim was to present a systematic review of the role of interleukins in vitiligo, focusing on interleukins. In this review, we included all studies assessing interleukin levels in vitiligo patients conducted up to June 2017. Quality assessment of these studies was performed using the Newcastle-Ottawa Scale (NOS). The interleukins mainly involved were IL-2, IL-4, IL-6, IL-10 and IL-17. The studies highlight the crucial role of IL-17 in the onset and progression of the disease, and its synergistic action with IL-2, IL-6 and IL-33. Dysregulated levels of the interleukins were also correlated with the stage of disease, the affected skin surface area, and indicated as the main factor for lymphocyte infiltration found in depigmented regions. These findings illustrate the growing need for new therapies targeting vitiligo and further research into the role of interleukins as an area of particular interest.

Critical appraisal of the oxidative stress pathway in vitiligo: a systematic review and meta-analysis

BACKGROUND

The pathogenesis of vitiligo remains a topic of extensive debate. This is partly due to the moderate efficacy of current treatments. The role of the oxidative stress pathway in vitiligo is a popular although controversial research topic.

OBJECTIVE

To clarify the role of the oxidative stress pathway in vitiligo compared to other inflammatory skin disorders and to assess the therapeutic role of antioxidants.

METHODS

We conducted a systematic search of the existing literature on the aberrancies of the oxidative stress pathway in vitiligo. Subsequently, the efficacy of both topical and oral antioxidants in clinical trials was investigated.

RESULTS

A deregulated oxidative pathway is clearly evident with elevated superoxide dismutase, decreased catalase and increased lipid peroxidation. However, similar results have been obtained in other inflammatory skin diseases such as psoriasis, atopic dermatitis, lichen planus and urticaria. This questions the unique role of oxidative stress in the development of vitiligo. Some isolated successes have been reported with oral ginkgo biloba, polypodium leucotomos and vitamin C and E preparations, while other clinical trials have failed to show reproducible results. The use of topical antioxidants delivers in general no beneficial results.

CONCLUSION

The oxidative pathway is affected in vitiligo, but its unique initiating or contributory role in the pathogenesis is less evident. Interesting data support the added value of oral antioxidants in vitiligo although confirmatory studies are missing.

Paradoxical Reactions to Biologic Therapy in Psoriasis: A Review of the Literature

Biologic drugs, which are molecules designed to act on specific immune system targets, have been shown to be very effective in treating various dermatological, rheumatological, and systemic diseases. As a group, they have an acceptable safety profile, but their use has been associated with the onset of both systemic and organ-specific inflammatory conditions. True paradoxical reactions are immune-mediated disorders that would usually respond to the biologic agent that causes them. There is still debate about whether certain other adverse reactions can be said to be paradoxical. The hypotheses proposed to explain the pathogenesis of such reactions include an imbalance in cytokine production, with an overproduction of IFN-α and altered lymphocyte recruitment and migration (mediated in part by CXCR3), and the production of autoantibodies. Some biologic therapies favor granulomatous reactions. While most of the paradoxical reactions reported have been associated with the use of TNF-α inhibitors, cases associated with more recently introduced biologic therapies -such as ustekinumab, secukinumab, and ixekizumab- are increasingly common. The study of paradoxical adverse events not only favors better management of these reactions in patients receiving biologic therapy, but also improves our knowledge of the pathogenesis of chronic inflammatory diseases and helps to identify potential therapeutic targets.

Dry Eye Assessment in Patients With Vitiligo

PURPOSE

To evaluate tear osmolarity and tear film parameters in patients with vitiligo.

METHODS

A total of 25 eyes of 25 patients with vitiligo with periocular involvement (group 1), 30 eyes of 30 patients with vitiligo without periocular involvement (group 2), and 20 eyes of 20 controls (group 3) were evaluated using the Ocular Surface Disease Index (OSDI) questionnaire, Schirmer I test, tear film breakup time, scoring of ocular surface fluorescein staining using a modified Oxford scale, and tear osmolarity.

RESULTS

Mean tear osmolarity was 332 ± 16.3 mOsm/L in group 1, 308.8 ± 19.5 mOsm/L in group 2, and 286.3 ± 23.4 mOsm/L in group 3 (P < 0.001). There was no significant difference in Schirmer I test results among the 3 groups (16.5 ± 3.2 mm in group 1, 16.3 ± 4.7 mm in group 2, and 17.4 ± 4.2 mm in group 3) (P = 0.175). Tear film breakup time measurements in groups 1 (9.8 ± 3.5 seconds) and 2 (10.1 ± 4.3 seconds) were significantly lower than those in group 3 (18.5 ± 4.0 seconds) (P < 0.001). There was no significant difference among the 3 groups on the Oxford scale (0.04 ± 0.70 in group 1, 0.03 ± 0.33 in group 2, and 0.03 ± 0.20 in group 3) (P = 0.865). The mean Ocular Surface Disease Index score was significantly higher in groups 1 and 2 than in group 3 (42.1 ± 16.5 in group 1, 39.9 ± 17.3 in group 2, and 12.3 ± 11.6 in group 3) (P < 0.001).

CONCLUSIONS

This study showed that vitiligo is associated with tear hyperosmolarity and tear film dysfunction. Patients with vitiligo with periocular involvement may be more prone to dry eye than those without ocular involvement.

IL-17 induces cellular stress microenvironment of melanocytes to promote autophagic cell apoptosis in vitiligo

Vitiligo is a depigmentary disorder that develops as a result of the progressive disappearance of epidermal melanocytes. Stress can precipitate or exacerbate a skin disease through psychosomatic mechanisms. Stress exposure induces vitiligo-like symptoms in mice, as cellular damage to melanocytes causes synthetic pigment loss. Stress also increases IL-17, IL-1β, and antimelanocyte IgG in model mouse serum. Up-regulation of the IL-1β transcript in patients suggests its possible role in autoimmune pathogenesis of vitiligo. We demonstrate that IL-17 promoted IL-1β secretion from keratinocytes. Mitochondrial dysfunction, which can induce the excessive production of reactive oxygen species (ROS), is emerging as a mechanism that underlies various inflammatory and autoimmune diseases. In this study, we demonstrate that IL-17 inhibits melanogenesis of zebrafish, normal human epidermal melanocytes, and B16F10 cells. IL-17 increased mitochondrial dysfunction and ROS accumulation, which was related to autophagy induction. Autophagy is needed for autophagic apoptosis of B16F10 cells induced by IL-17. To inhibit ROS generation, B16F10 cells were pretreated with N-acetyl-l-cysteine (NAC), which inhibited autophagy. 3-Methyladenine (3-MA) also had an inhibiting effect on autophagy. NAC or 3-MA pretreatments inhibited IL-17-mediated cell apoptosis. In summary, IL-17 induces the cellular stress microenvironment in melanocytes to promote autophagic cell apoptosis in vitiligo.-Zhou, J., An, X., Dong, J., Wang, Y., Zhong, H., Duan, L., Ling, J., Ping, F., Shang, J. IL-17 induces cellular stress microenvironment of melanocytes to promote autophagic cell apoptosis in vitiligo.

Evaluation of treatment response to autologous transplantation of noncultured melanocyte/keratinocyte cell suspension in patients with stable vitiligo

Background

Vitiligo is a chronic disease characterized by the appearance of achromic macules caused by melanocyte destruction. Surgical treatments with melanocyte transplantation can be used for stable vitiligo cases.

Objectives

To evaluate treatment response to the autologous transplantation of noncultured epidermal cell suspension in patients with stable vitiligo.

Methods

Case series study in patients with stable vitiligo submitted to noncultured epidermal cell suspension transplantation and evaluated at least once, between 3 and 6 months after the procedure, to observe repigmentation and possible adverse effects. The maximum follow-up period for some patients was 24 months.

Results

Of the 20 patients who underwent 24 procedures, 25% showed an excellent rate of repigmentation, 50% good repigmentation, 15% regular, and 10% poor response. The best results were observed in face and neck lesions, while the worst in extremity lesions (88% and 33% of satisfactory responses, respectively). Patients with segmental vitiligo had a better response (84%) compared to non-segmental ones (63%). As side effects were observed hyperpigmentation of the treated area and the appearance of Koebner phenomenon in the donor area.

Study limitations

Some limitations of the study included the small number of patients, a subjective evaluation, and the lack of long-term follow-up on the results. CONCLUSION: Noncultured epidermal cell suspension transplantation is efficient and well tolerated for stable vitiligo treatment, especially for segmental vitiligo on the face and neck.

The early repigmentation pattern of vitiligo is related to the source of melanocytes and by the choice of therapy: a retrospective cohort study

BACKGROUND

Patients with vitiligo present with different repigmentation patterns in the early recovery stage.

OBJECTIVES

To analyze the relationships between early repigmentation patterns in vitiliginous patches, their clinical characteristics, and therapeutic choices.

METHODS

Patients with vitiligo seen in the Department of Dermatology, The First Affiliated Hospital of Nanjing Medical University from 2010 to 2015, were included, and their clinical records, especially photographs and medical treatments, were reviewed.

RESULTS

One hundred and sixteen patients were included in this study, and 326 lesions with different degrees of depigmentation, locations, stages, distributions, therapies, and repigmentation patterns were included and analyzed. Perifollicular repigmentation occurred more frequently in lesions with complete depigmentation (P = 0.005), in non-sun exposed areas (P < 0.001), a stable stage (P = 0.008), and lesions treated with narrow band ultraviolet B (NB-UVB) (P < 0.001, despite lesion distributions). Marginal repigmentation is more frequent in lesions with complete depigmentation (P = 0.016), lesions treated without NB-UVB (P = 0.002), and facial lesions treated with topical vitamin D analogs (TVDAs) monotherapy (P = 0.022). Diffuse repigmentation is the predominant pattern in lesions with incomplete depigmentation (P < 0.001), in sun-exposed areas (P < 0.001), progressive stage (P = 0.044), and truncal lesions treated with TVDAs (P < 0.001).

CONCLUSIONS

The different repigmentation patterns of vitiligo lesions depend on the different source and status of melanocytes and their abilities to produce melanin on the choice of therapy.

Vitiligo: An Update on Pathophysiology and Treatment Options

The pathophysiology of vitiligo is becoming increasingly clarified. In non-segmental vitiligo, early factors include activation of innate immunity, inflammasome activation, oxidative stress, and loss of melanocyte adhesion. Nonetheless, the main mechanism leading to non-segmental vitiligo involves an immune-mediated destruction of melanocytes. Anti-melanocyte-specific cytotoxic T cells exert a central role in the final effector stage. Genetic research revealed a multi-genetic inheritance displaying an overlap with other autoimmune disorders. However, some melanocyte-specific genes were also affected. Segmental vitiligo carries a different pathogenesis with most evidence indicating a mosaic skin disorder. Current management includes topical corticosteroids and immunomodulators. Narrow-band ultraviolet B can be used in patients not responding to topical treatment or in patients with extensive disease. Pigment cell transplantation offers an alternative for the treatment of segmental vitiligo or stable non-segmental lesions. Recent findings have revealed new targets for treatment that could lead to more efficient therapies. Targeted immunotherapy may halt the active immune pathways, although combination therapy may still be required to induce satisfying repigmentation. A recently established core set of outcome measures, new measurement instruments, and biomarker research pave the way for future standardized clinical trials.

Phototherapy and Combination Therapies for Vitiligo

Vitiligo is a disease characterized by disappearance of melanocytes from the skin. It can negatively influence the physical appearance of affected individuals, and may profoundly affect a person's psychosocial function and quality of life. Therefore, vitiligo should not be considered as merely a condition that affects a patient's appearance, but needs to be actively treated in patients who seek medical help. Phototherapy has been used as the main treatment modality for patients with vitiligo. Different forms of phototherapy for vitiligo include broadband UVB, narrowband UVB, excimer light and excimer laser, and psoralen plus UVA.

Biomarkers of disease activity in vitiligo: A systematic review

The pathophysiology of vitiligo is complex although recent research has discovered several markers which are linked to vitiligo and associated with disease activity. Besides providing insights into the driving mechanisms of vitiligo, these findings could reveal potential biomarkers. Activity markers can be used to monitor disease activity in clinical trials and may also be useful in daily practice. The aim of this systematic review was to document which factors have been associated with vitiligo activity in skin and blood. A second goal was to determine how well these factors are validated in terms of sensitivity and specificity as biomarkers to determine vitiligo activity. Both in skin (n=43) as in blood (n=66) an adequate number of studies fulfilled the predefined inclusion criteria. These studies used diverse methods and investigated a broad range of plausible biomarkers. Unfortunately, sensitivity and specificity analyses were scarce. In skin, simple histopathology with or without supplemental CD4 and CD8 stainings can still be considered as the gold standard, although more recently chemokine (C-X-C motif) ligand (CXCL) 9 and NLRP1 have demonstrated a good and possibly even better association with progressive disease. Regarding circulating biomarkers, cytokines (IL-1β, IL-17, IFN-γ, TGF-β), autoantibodies, oxidative stress markers, immune cells (Tregs), soluble CDs (sCD25, sCD27) and chemokines (CXCL9, CXCL10) are still competing. However, the two latter may be preferable as both chemokines and soluble CDs are easy to measure and the available studies display promising results. A large multicenter study could make more definitive statements regarding their sensitivity and specificity.

Identification of chemical components in Baidianling Capsule based on gas chromatography-mass spectrometry and high-performance liquid chromatography combined with Fourier transform ion cyclotron resonance mass spectrometry

Baidianling Capsule, which is made from 16 Chinese herbs, has been widely used for treating vitiligo clinically. In this study, the sensitive and rapid method has been developed for the analysis of chemical components in Baidianling Capsule by gas chromatography-mass spectrometry in combination with retention indices and high-performance liquid chromatography combined with Fourier transform ion cyclotron resonance mass spectrometry. Firstly, a total of 110 potential volatile compounds obtained from different extraction procedures including alkanes, alkenes, alkynes, ketones, ethers, aldehydes, alcohols, phenols, organic acids, esters, furans, pyrrole, acid amides, heterocycles, and oxides were detected from Baidianling Capsule by gas chromatography-mass spectrometry, of which 75 were identified by mass spectrometry in combination with the retention index. Then, a total of 124 components were tentatively identified by high-performance liquid chromatography combined with Fourier transform ion cyclotron resonance mass spectrometry. Fifteen constituents from Baidianling Capsule were accurately identified by comparing the retention times with those of reference compounds, others were identified by comparing the retention times and mass spectrometry data, as well as retrieving the reference literature. This study provides a practical strategy for rapidly screening and identifying the multiple constituents of a complex traditional Chinese medicine.

Construction of a Comprehensive Protein-Protein Interaction Map for Vitiligo Disease to Identify Key Regulatory Elements: A Systemic Approach

Vitiligo is an idiopathic disorder characterized by depigmented patches on the skin due to progressive loss of melanocytes. Several genetic, immunological, and pathophysiological investigations have established vitiligo as a polygenetic disorder with multifactorial etiology. However, no definite model explaining the interplay between these causative factors has been established hitherto. Therefore, we studied the disorder at the system level to identify the key proteins involved by exploring their molecular connectivity in terms of topological parameters. The existing research data helped us in collating 215 proteins involved in vitiligo onset or progression. Interaction study of these proteins leads to a comprehensive vitiligo map with 4845 protein nodes linked with 107,416 edges. Based on centrality measures, a backbone network with 500 nodes has been derived. This has presented a clear overview of the proteins and processes involved and the crosstalk between them. Clustering backbone proteins revealed densely connected regions inferring major molecular interaction modules essential for vitiligo. Finally, a list of top order proteins that play a key role in the disease pathomechanism has been formulated. This includes SUMO2, ESR1, COPS5, MYC, SMAD3, and Cullin proteins. While this list is in fair agreement with the available literature, it also introduces new candidate proteins that can be further explored. A subnetwork of 64 vitiligo core proteins was built by analyzing the backbone and seed protein networks. Our finding suggests that the topology, along with functional clustering, provides a deep insight into the behavior of proteins. This in turn aids in the illustration of disease condition and discovery of significant proteins involved in vitiligo.

An ongoing role for Wnt signaling in differentiating melanocytes in vivo

A role for Wnt signaling in melanocyte specification from neural crest is conserved across vertebrates, but possible ongoing roles in melanocyte differentiation have received little attention. Using a systems biology approach to investigate the gene regulatory network underlying stable melanocyte differentiation in zebrafish highlighted a requirement for a positive-feedback loop involving the melanocyte master regulator Mitfa. Here, we test the hypothesis that Wnt signaling contributes to that positive feedback. We show firstly that Wnt signaling remains active in differentiating melanocytes and secondly that enhanced Wnt signaling drives elevated transcription of mitfa. We show that chemical activation of the Wnt signaling pathway at early stages of melanocyte development enhances melanocyte specification as expected, but importantly that at later (differentiation) stages, it results in altered melanocyte morphology, although melanisation is not obviously affected. Downregulation of Wnt signaling also results in altered melanocyte morphology and organization. We conclude that Wnt signaling plays a role in regulating ongoing aspects of melanocyte differentiation in zebrafish.

Repigmentation patterns induced by NB-UVB and their relationship with melanocytic migration and proliferation in vitiligo

BACKGROUND/PURPOSE

Vitiligo is the most commonly acquired depigmentation disorder of the skin and is characterized by the destruction of melanocytes. Ultraviolet phototherapy with narrow band (UVB-NB) induces proliferation, differentiation, maturation, and migration of melanocytes. The clinical repigmentation is featured by follicular, marginal, and diffuse patterns. The aim of this study was to observe the process involved in the melanocyte migration and proliferation among these patterns and the unresponsive lesions following UVB-NB phototherapy. The focal adhesion kinase (FAK) and c-KIT were used as markers of melanocyte migration and differentiation, respectively.

METHODS

A total of 17 vitiligo patients under UVB-NB therapy were selected. The patients expressed the three repigmentation patterns as well as unresponsive lesions at the conclusion of a 30-session cycle. Skin biopsies were evaluated by immunohistochemistry and qRT-PCR.

RESULTS

We found an increased expression of c-KIT in the follicular pattern compared to the diffuse pattern that was expressed predominantly of FAK. Marginal pattern expressed both proteins. The unresponsive achromic lesions showed poor expressions of both markers.

CONCLUSION

Proliferation was prominent in the follicular pattern, but migration was prominent in the diffuse pattern. For the marginal pattern, both dynamics were present. The absence of these markers in vitiligo lesions suggests a lack of response to UVB-NB.

Targeting CTLA-4, PD-L1 and IDO to modulate immune responses in vitiligo

For decades, an extensive debate is continued on the pathophysiology of vitiligo. Numerous hypotheses have been put forward, and many supported by well-documented arguments. Regardless of the initiating steps, most experts agree that an immune-based melanocyte destruction is responsible for the final steps leading to epidermal depigmentation. It is remarkable that currently the only therapeutic approach to counter this phenomenon consists of non-specific local and systemic immunosuppressants. Immunotherapy for melanoma reveals that targeting factors involved in peripheral tolerance are sufficient to break the natural defense mechanisms to develop skin depigmentations. Therapeutically enhancing these immune checkpoints seems therefore a promising long-term therapy for vitiligo. In this viewpoint, we propose this strategy as a promising therapeutic option for vitiligo. Several approaches are proposed with a focus on cytotoxic T-lymphocyte-associated protein 4, programmed death ligand-1 and indoleamine 2,3-dioxygenase.

Phototherapy: The vitiligo management pillar

Phototherapy has been the mainstay of vitiligo therapy for several decades. A variety of wavelengths and modalities are available, but narrowband ultraviolet B remains the safest and most commonly used treatment. Acting on multiple steps in vitiligo pathogenesis, narrowband ultraviolet B is one of the few therapies that can effectively induce stabilization and stimulate repigmentation. Achievement of optimal results involves using a combination of appropriate treatment protocols, careful patient selection, and patient education to set expectations. Individual patient characteristics, including disease activity, vitiligo phenotype, lesion location, and skin phototype, should all be considered, along with combination therapies.

Interleukin 10 protects primary melanocyte by activation of Stat-3 and PI3K/Akt/NF-κB signaling pathways

Vitiligo is a common melanocytopenic disorder of the skin, with acquired focal depigmentation. Normal human skin relies on melanocytes to provide photoprotection and thermoregulation by producing melanin. Interleukin 10 (IL-10) is a pleiotropic immunoregulatory cytokine drawing more and more researchers' attention. The present study was conducted to investigate the effects of IL-10 on melanocytes and elucidate the underlying mechanisms. We proved that IL-10 play no role in regulating melanogenesis of normal human foreskin-derived epidermal melanocytes (NHEM). IL-10 stimulation activated the JAK/Stat-3 and PI3K/Akt signaling pathways. Moreover, IL-10 treatment increased translocation of p65 NF-κB into the nuclear compartment, and up-regulated expression of the pro-survival proteins Bcl-2 and Bcl-xL. IL-10 restored anti-apoptotic proteins expression and suppressed cytochrome c release in H2O2-induced apoptosis. In conclusion, IL-10 may provide pro-survival cues to melanocytes and be applied in the treatment of vitiligo and other depigmenting disorders.

[Treatment of vitiligo]

The range of treatment options for vitiligo has significantly expanded in the last 10 years and we can offer our patients more effective treatment strategies supported by European guidelines and consensus findings. Topical and UV therapy are-often in combination-the main components of vitiligo treatment. The main outcome parameters include extent and maintenance of gained repigmentation, cessation of spreading, avoidance of side effects and the influence of the treatment on the quality of life. The efficacy of the currently available treatments is often limited. New options include antioxidative or melanocyte-stimulating adjuvant therapies in combination with UV or laser light as well as a topical maintenance treatment to reduce the risk of recurrences. In many cases, psychological support is indicated.

Efficacy and Safety of 308-nm Monochromatic Excimer Lamp Versus Other Phototherapy Devices for Vitiligo: A Systematic Review with Meta-Analysis

BACKGROUND

Various phototherapy methods are used to treat vitiligo; however, the recent emergence of new devices has heightened debate concerning the best treatment method.

OBJECTIVE

We aimed to systematically review and meta-analyze published data comparing the efficacy and adverse effects of monochromatic excimer lamps versus excimer laser and narrowband ultraviolet B (NB-UVB) in treating vitiligo.

METHODS

A systematic search of PubMed, EMBASE, LILACS, Cochrane Central Register of Controlled Trials (CENTRAL), and clinical trials registries identified randomized controlled trials that included vitiligo patients, regardless of age, sex, or study language. We evaluated studies comparing excimer lamps with excimer laser or NB-UVB phototherapy.

RESULTS

The review included six studies (411 patients, 764 lesions). No study found significantly different efficacy between excimer lamps and excimer laser using the outcomes of ≥50% repigmentation [risk ratio (RR) = 0.97, 95% confidence interval (CI) 0.84-1.11] and ≥75% repigmentation (RR = 0.96, 95% CI 0.71-1.30). Likewise, no study found significant differences between excimer lamps and NB-UVB (RR = 1.14, 95% CI 0.88-1.48 for ≥50% repigmentation; RR = 1.81, 95% CI 0.11-29.52 for ≥75% repigmentation). Adverse effects were mild, including pruritus, burning sensation, and dryness, none of which interrupted treatment.

CONCLUSIONS

To our knowledge, this is the first systematic review of the efficacy and safety of excimer lamp treatment for vitiligo. Excimer lamps, excimer laser, and NB-UVB are all safe and effective in repigmentation of vitiligo lesions. Safety, effectiveness, and cost are considerations when choosing treatment.

PROSPERO REGISTRATION NUMBER

CRD42014015237.

Immunological Parameters Associated With Vitiligo Treatments: A Literature Review Based on Clinical Studies

Vitiligo, a depigmentary disorder, caused by the loss of melanocytes, affects approximately 1% of the world population, irrespective of skin type, with a serious psychological impact on the patient quality of life. So far, the origin of vitiligo has not been traced and the pathogenesis is complex, involving the interplay of a multitude of variables. Although there is no treatment that ensures the complete cure of the disorder, there are some pharmacological, phototherapy, and surgical therapies available. A series of variables can affect treatment outcome, such as individual characteristics, emotional issues, type of vitiligo, stability of the lesions, and immunological status. The present literature review identified the main immunological parameters associated with treatments for vitiligo. Cytotoxic CD8+ T lymphocytes are the main cell type involved in treatment success, as fewer cells in skin lesions are associated with better results. Other parameters such as cytokines and regulatory T cells may also be involved. Further clinical scientific studies are needed to elucidate the complex mechanisms underlying vitiligo and its treatments, in order to expand the range of therapeutic approaches for each individual case.

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.

Tumour necrosis factor-α inhibition can stabilize disease in progressive vitiligo

Tumour necrosis factor (TNF)-α, a proinflammatory cytokine central to many autoimmune diseases, has been implicated in the depigmentation process in vitiligo. We review its role in vitiligo by exploring its pro- and anti-inflammatory properties and examine the effects of blocking its actions with TNF-α antagonist therapeutics in reports available in the literature. We found that TNF-α inhibition halts disease progression in patients with progressive vitiligo but that, paradoxically, treatment can be associated with de novo vitiligo development in some patients when used for other autoimmune conditions, particularly when using adalimumab and infliximab. These studies reinforce the importance of stating appropriate outcomes measures, as most pilot trials propose to measure repigmentation, whereas halting depigmentation is commonly overlooked as a measure of success. We conclude that TNF-α inhibition has proven useful for patients with progressive vitiligo, where TNF-α inhibition is able to quash cytotoxic T-cell-mediated melanocyte destruction. However, a lingering concern for initiating de novo disease will likely prevent more widespread application of TNF inhibitors to treat vitiligo.