Vitiligo: where do we stand?

100 Most-Cited Articles in Vitiligo: A Bibliometric Analysis

Introduction

Vitiligo is a skin disease affecting melanocytes, characterised by the development of depigmented skin lesions.

Methods

We used bibliometric analysis (BA) to identify high-quality research articles on vitiligo using criteria such as total citations, annual citations (AC) and journal impact factors. We extracted the 100 most-cited articles on vitiligo using the Web of Science database and analysed the results using Microsoft Excel 2019. Our search was limited to manuscript titles or abstracts containing the keyword 'vitiligo'. The data extracted information such as title, author, year of publication, journal of publication, total citations and research area. We also calculated the AC rate to account for bias.

Results

A total of 6,189 studies were retrieved. The 100 most-cited articles were published between 1976 and 2017. Of those, 75 were original articles, with the research foci being mainly pathogenesis (29%) and treatment (26%). The US was the most prolific publisher overall. We separately retrieved the highest cited data from 2018 to 2022 and tabled the top 10. Of those, 50% were original articles.

Discussion

Our BA shows that developed countries published most of the vitiligo literature. Additionally, recent research has focused on targeted treatment approaches. We also highlight the increasing paediatric vitiligo research, specifically regarding therapies.

Endoplasmic Reticulum Dysfunction: An Emerging Mechanism of Vitiligo Pathogenesis

The endoplasmic reticulum (ER) is the main site of protein synthesis, transport, and modification. Its abnormal status has now emerged as an established cause of many pathological processes, such as tumors and autoimmune diseases. Recent studies also demonstrated that the defective functions of ER may lead to pigmentary diseases. Vitiligo is a depigmenting ailment skin disorder whose pathogenesis is now found to be associated with ER. However, the detailed mechanism is still unclear. In this review, we try to link the association between ER with its inter- and intra-organellar interactions in vitiligo pathogenesis and focus on the function, mechanism, and clinical potential of ER with vitiligo. Expand ER is found in melanocytes of vitiligo and ER stress (ERS) might be a bridge between oxidative stress and innate and adaptive immunity. Meanwhile, the tight association between ER and mitochondria or melanosomes in organelles levels, as well as genes and cytokines, is the new paradigm in the pathogenesis of vitiligo. This undoubtedly adds a new aspect to the understanding of vitiligo, facilitating the design of targeted therapies for vitiligo.

The Immunogenetics of Vitiligo: An Approach Toward Revealing the Secret of Depigmentation

Vitiligo is a hypomelanotic skin disease and considered to be of autoimmune origin due to breaching of immunological self-tolerance, resulting in inappropriate immune responses against melanocytes. The development of vitiligo includes a strong heritable component. Different strategies ranging from linkage studies to genome-wide association studies are used to explore the genetic factors responsible for the disease. Several vitiligo loci containing the respective genes have been identified which contribute to vitiligo and genetic variants for some of the genes are still unknown. These genes include mainly the proteins that play a role in immune regulation and a few other genes important for apoptosis and regulation of melanocyte functions. Despite the available data on genetic variants and risk alleles which influence the biological processes, only few immunological pathways have been found responsible for all ranges of severity and clinical manifestations of vitiligo. However, studies have concluded that vitiligo is of autoimmune origin and manifests due to complex interactions in immune components and their inappropriate response toward melanocytes. The genes involved in the immune regulation and processing the melanocytes antigen and its presentation can serve as effective immune-therapeutics that can target specific immunological pathways involved in vitiligo. This chapter highlights those immune-regulatory genes involved in vitiligo susceptibility and loci identified to date and their implications in vitiligo pathogenesis.

Association of vitiligo with high-frequency sensorineural hearing loss: a systematic review and meta-analysis

The association between vitiligo and hearing loss has been noted but the specific frequencies and degrees of hearing impairment remain unclear. The objective of this systematic review was to investigate the relationship between vitiligo and hearing thresholds at various specific frequencies. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We searched MEDLINE and Embase for relevant studies from inception to 10th April 2021. Case-control studies, cross-sectional, or cohort studies that compared the frequency-specific hearing thresholds between vitiligo patients and age-matched non-vitiligo controls were included. There were neither language nor geographic limitations. We used the Newcastle-Ottawa Scale to assess the risk of bias of included studies. The DerSimonian and Laird random-effects model was utilized in meta-analyses due to expected clinical heterogeneity. We included 9 case-control studies with 371 vitiligo patients and 349 controls, which were rated with low or unclear risk. We found neither relevant cross-sectional nor cohort studies. The meta-analysis showed that when compared with controls, vitiligo patients had significantly higher pure-tone hearing thresholds at 2000, 4000, and 8000 Hz. In conclusions, vitiligo patients are prone to high-frequency sensorineural hearing loss.

Is targeted UVB as effective as excimer light phototherapy in treatment of vitiligo?

Excimer light (EL) and targeted UVB (TUVB) devices have been used successfully in repigmenting vitiligo. To compare the repigmenting efficacy and safety of EL with TUVB device in vitiligo. The study was conducted retrospectively on patients of vitiligo who had received either EL (Group A) or TUVB (Group B) from year 2015 to 2020. Data pertaining to 40 such age and sex matched patients from each group was retrieved with almost similar sites of involvement. Only patients whose phototherapy sessions had been given twice weekly for minimum of 30 sessions or until 90%-100% repigmentation were included in the study. The study was retrospective in nature and the principles outlined in the Declaration of Helsinki were followed during the study. The primary endpoint compared between the two groups was the extent of repigmentation achieved on different sites of body and adverse effects from treatment. Secondary endpoints compared included total number of doses, cumulative dose needed for complete repigmentation and number of doses needed for onset of repigmentation. There were 82.6% responders in Group A and 76.3% in Group B who had achieved at least 50% repigmentation. Excellent response (75%-100% repigmentation) was achieved in 68.1% lesions in Group A and 46.4% lesions in Group B. Patients in Group A needed less number of doses (13.75 vs. 19.37) and less cumulative dose (6.14 vs. 7.69 J/cm² ) to achieve complete or near complete repigmentation. Adverse effects were negligible in both groups. Targeted phototherapy with EL demonstrated better repigmenting efficacy than TUVB in vitiligo.

Assessment of auditory and vestibular functions in vitiligo patients

Objectives

To evaluate audiological and vestibular functions via basic audiological evaluation, otoacoustic emissions and videonystagmography (VNG) in vitiligo patients.

Material and methods

30 vitiligo patients (8 acrofacial and 22 mixed types) as the study group and 30 normal healthy adults as the control group were included in the study. All participants were submitted to basic audiological evaluation, transient and distortion product otoacoustic emmisions (TEOAEs and DPOAEs), vestibular assessment including history taking, office tests and videonystagmography (VNG) and dermatological assessment to determine type, percent of body surface area involvement and duration of vitiligo.

Results

This study showed statistically significant difference between control and study groups in pure tone audiometry (PTA) and otoacoustic emissions results. Fifty percent of vitiligo patients had peripheral vestibular disorders (10 vestibular neuritis and 5 posterior canal benign paroxysmal positional vertigo.

Conclusion

The results in this study showed that 50% of vitiligo patients suffered from peripheral vestibular disorders in addition to auditory affection. Vitiligo patients require routine monitoring for auditory and vestibular functions for early identification and monitoring of changes as the disease progress.

The Effect of Butin on the Vitiligo Mouse Model Induced by Hydroquinone

Vernonia anthelmintica (L.) Willd has been traditionally used in the treatment of vitiligo in Uyghur medicine. This study used butin, the main component of V. anthelmintica, to study the influence on hydroquinone-induced vitiligo in mice. The animals were randomly divided into six groups: control, model, 8-methoxypsoralen (8-MOP, 4.25 mg/kg), and butin (0.425, 4.25, and 42.5 mg/kg) groups. The number of melanin-containing hair follicles, basal layer melanocytes, melanin-containing epidermal cells, the expression of tyrosinase (TYR) and tyrosinase-related protein-1 (TRP-1), the malondialdehyde (MDA), and cholinesterase (CHE) activity in serum were measured. Our results indicated that compared with the model group, the melanin-containing hair follicles, the expression of TYR and TRP-1 increased, the activity of CHE decreased after treatment with 8-MOP and all doses of butin (p < 0.05, p < 0.01), the basal layer melanocytes and melanin-containing epidermal cells increased significantly after treatment with butin 4.25 and 42.5 mg/kg (p < 0.05, p < 0.01), and the MDA activity decreased after using butin 4.25 and 42.5 mg/kg and 8-MOP (p < 0.05, p < 0.01). Our results support the use of butin on vitiligo, and its possible mechanisms may be related to increase the TYR and TRP-1 protein expression and decrease the activity of MDA and CHE in hydroquinone-induced vitiligo model in mice. Copyright © 2017 John Wiley & Sons, Ltd.

Oxidative stress drives CD8+ T-cell skin trafficking in patients with vitiligo through CXCL16 upregulation by activating the unfolded protein response in keratinocytes

BACKGROUND

In patients with vitiligo, an increased reactive oxygen species (ROS) level has been proved to be a key player during disease initiation and progression in melanocytes. Nevertheless, little is known about the effects of ROS on other cells involved in the aberrant microenvironment, such as keratinocytes and the following immune events. CXCL16 is constitutively expressed in keratinocytes and was recently found to mediate homing of CD8⁺ T cells in human skin.

OBJECTIVE

We sought to explicate the effect of oxidative stress on human keratinocytes and its capacity to drive CD8⁺ T-cell trafficking through CXCL16 regulation.

METHODS

We first detected putative T-cell skin-homing chemokines and ROS in serum and lesions of patients with vitiligo. The production of candidate chemokines was detected by using quantitative real-time PCR and ELISA in keratinocytes exposed to H₂O₂. Furthermore, the involved mediators were analyzed by using quantitative real-time PCR, Western blotting, ELISA, and immunofluorescence. Next, we tested the chemotactic migration of CD8⁺ T cells from patients with vitiligo mediated by the CXCL16-CXCR6 pair using the transwell assay.

RESULTS

CXCL16 expression increased and showed a positive correlation with oxidative stress levels in serum and lesions of patients with vitiligo. The H₂O₂-induced CXCL16 expression was due to the activation of 2 unfolded protein response pathways: kinase RNA (PKR)-like ER kinase-eukaryotic initiation factor 2α and inositol-requiring enzyme 1α-X-box binding protein 1. CXCL16 produced by stressed keratinocytes induced migration of CXCR6⁺CD8⁺ T cells derived from patients with vitiligo. CXCR6⁺CD8⁺ T-cell skin infiltration is accompanied by melanocyte loss in lesions of patients with vitiligo.

CONCLUSION

Our study demonstrated that CXCL16-CXCR6 mediates CD8⁺ T-cell skin trafficking under oxidative stress in patients with vitiligo. The CXCL16 expression in human keratinocytes induced by ROS is, at least in part, caused by unfolded protein response activation.

Blood supply--susceptible formation of melanin pigment in hair bulb melanocytes of mice

BACKGROUND

Allogeneic skin grafts onto C57BL/6 mice are rejected, and the rejected skin is replaced by surrounding skin with black hair. In contrast, syngeneic skin grafts are tolerated, and gray hair grows on the grafts.

METHODS

To explore the mechanism of gray hair growing on the tolerated skin grafts, we prepared full-thickness skin (2-cm square) autografts, 2 (2 cm + 2 cm) horizontal or vertical parallel incisions, and U-shaped (2 cm × 2 cm × 2 cm) flaps with or without pedicle vessels. The grafts, incisions, and flaps were fixed by suturing with string and protected by a transparent bandage. On day 14 after the operation, the bandages were removed to observe the color of the hair growing on the skin.

RESULTS

Skin autografts from wild-type or hepatocyte growth factor-transgenic (Tg) C57BL/6 mice survived with gray hair, whereas those from steel factor (Kitl)-Tg C57BL/6 mice survived with black hair. In addition, U-shaped flaps lacking both of the 2 main feeding vessels of wild-type mice had gray hair at the tip of the flaps. Light microscopy after staining with hematoxylin and eosin or dihydroxyphenylalanine showed that the formation of melanin pigment in the follicles, but not in the interadnexal skin, was susceptible to the blood supply.

CONCLUSIONS

Melanin pigment formation in the hair bulb melanocytes appeared to be susceptible to the blood supply, and melanocytosis was promoted in the follicles and in the epidermis of Kitl-Tg C57BL/6 mice.

Current aspects of vitiligo genetics

Vitiligo is a common acquired depigmentation disorder of the skin manifested by the presence of white macules. The disease occurs at a frequency of approximately 1–4% of the world population. Currently, the most popular theory of vitiligo development is a multifactorial hypothesis according to which genetic conditions predispose vitiligo macules to occur as a result of specific environmental factors. According to the genetic hypothesis, vitiligo inheritance is multigenic. Genetic studies conducted so far concern patients with non-segmental vitiligo. There are three basic techniques of genetic studies: candidate gene association studies, genomewide linkage studies and genome-wide association studies (GWAS). The GWAS are the “gold standard” for detecting susceptibility genes. Up to now, approximately 36 convincing non-segmental vitiligo susceptibility loci have been identified. Approximately 90% of them encode immunoregulatory proteins, while approximately 10% encode melanocyte proteins. The existence of various associations between vitiligo and other autoimmune diseases may provide new knowledge on the causes of many disorders. Examples include the inverse relationship between vitiligo and melanoma and association of vitiligo with other autoimmune diseases. The main goal of all researches is to find new, optimal therapeutic strategies for vitiligo and other autoimmune diseases.

Gingival vitiligo: report of a case and review of the literature

Rarely cases have been reported regarding depigmented lesions of the oral cavity. On reviewing the literature, only few cases of gingival vitiligo or similar lesions have been reported till date. These lesions pose a cosmetic challenge. We present here a case of vitiligo affecting gingiva. Vitiligo has been defined as an acquired, slowly progressive loss of cutaneous pigment which occurs as irregular, sharply defined patches which may or may not be surrounded by macroscopic hyperpigmentation. Differential diagnosis, detailed clinical history, histopathology, immunohistochemistry, and pathogenesis of this condition are discussed.

Involvement of superoxide dismutase isoenzymes and their genetic variants in progression of and higher susceptibility to vitiligo

Oxidative stress has been implicated as the initial triggering event in vitiligo pathogenesis leading to melanocyte destruction. Here, we report a significant increase in oxidative stress in vitiligo patients as evidenced by high lipid peroxidation levels suggesting an imbalance in the antioxidant enzyme system as reported in our previous studies. This study examined the role of the enzymatic antioxidant SOD, which converts the pro-oxidant superoxide into H2O2, in vitiligo pathogenesis. The activity of three isoforms of SOD, i.e., SOD1, SOD2, and SOD3, was significantly higher in vitiligo patients. To identify the underlying mechanism for the increase in activities of SOD isoforms, we explored the SOD1, SOD2, and SOD3 genes for their genetic variations and transcript levels. The SOD2 Thr58Ile (rs35289490) and Leu84Phe (rs11575993) polymorphisms were significantly associated with vitiligo patients, and the Val16Ala (rs4880) polymorphism was associated with active vitiligo patients. Interestingly, SOD2 activity was contributed by these polymorphisms along with its increase in transcript levels in patients. SOD3 activity was associated with the Arg213Gly (rs8192291) polymorphism. The SOD3 transcript levels were also increased in patients, which might contribute to the increased SOD3 activity. However, we could not establish the genotype-phenotype correlation for SOD1 as we could not detect any novel or reported SNPs in SOD1. In addition, both transcript and protein levels of SOD1 were unchanged between patients and controls, though SOD1 activity was increased in patients. Activities of SOD isoforms also correlated with progression of the disease as the activity was higher in active cases of vitiligo compared to stable cases. Here, we report that SOD2 and SOD3 polymorphisms may be genetic risk factors for susceptibility and progression of vitiligo and hence the genetic makeup of an individual may form a basis for the effective treatment of the disease. Overall, our results suggest that increased activity of SOD isoforms under the influence of genetic factors may lead to accumulation of H2O2 in cytoplasmic, mitochondrial, and extracellular compartments resulting in oxidative damage to the melanocytes.

Correlation of increased MYG1 expression and its promoter polymorphism with disease progression and higher susceptibility in vitiligo patients

BACKGROUND

MYG1 (Melanocyte proliferating gene 1 or C12orf10) -119C/G promoter and Arg4Gln structural polymorphisms have a functional impact on its regulation. The promoter polymorphism was shown to be associated with vitiligo in Caucasian population.

OBJECTIVE

The present study explores MYG1 polymorphisms and correlates them with MYG1 mRNA expression, disease onset and progression in vitiligo patients.

METHODS

Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used for genotyping of MYG1 -119C/G promoter (rs1465073) and 11-12AA/GC structural polymorphisms (rs1534284-rs1534283; Arg4Gln) in 846 vitiligo patients and 726 age-matched unaffected controls. MYG1 mRNA levels were assessed in whole blood of 166 patients and 175 controls by Real-time PCR.

RESULTS

The MYG1 -119C/G promoter polymorphism was found to be in significant association with vitiligo being 'G' allele prevalent in patients. However, 11-12AA/GC structural polymorphism was prevalently monogenic in patients and controls with only MYG1 GC (4Arg) allele being present. Significant increase in MYG1 mRNA expression was observed in vitiligo patients compared to controls. The MYG1 mRNA expression was increased in patients with active and generalized vitiligo as compared to stable and localized vitiligo. MYG1 mRNA expression was increased in patients with susceptible -119 GG genotype compared to controls. Also, patients with susceptible -119 GG genotype had early age of onset of vitiligo. Moreover, patients with age groups 1-20 years and 21-40 years showed increased expression of MYG1 mRNA compared to those of controls. Female patients showed significant increase in MYG1 mRNA and early age of onset of vitiligo compared to male patients.

CONCLUSION

The present study suggests that MYG1 -119C/G promoter polymorphism may be a genetic risk factor for susceptibility and progression of vitiligo. The up-regulation of MYG1 transcript in patients with susceptible -119GG genotype advocates the crucial role of MYG1 in autoimmune pathogenesis of vitiligo.

Vitiligo: interplay between oxidative stress and immune system

Vitiligo is a multifactorial polygenic disorder with a complex pathogenesis, linked with both genetic and non-genetic factors. The precise modus operandi for vitiligo pathogenesis has remained elusive. Theories regarding loss of melanocytes are based on autoimmune, cytotoxic, oxidant-antioxidant and neural mechanisms. Reactive oxygen species (ROS) in excess have been documented in active vitiligo skin. Numerous proteins in addition to tyrosinase are affected. It is possible that oxidative stress is one among the main principal causes of vitiligo. However, there also exists ample evidence for altered immunological processes in vitiligo, particularly in chronic and progressive conditions. Both innate and adaptive arms of the immune system appear to be involved as a primary event or as a secondary promotive consequence. There is speculation on the interplay, if any, between ROS and the immune system in the pathogenesis of vitiligo. The article focuses on the scientific evidences linking oxidative stress and immune system to vitiligo pathogenesis giving credence to a convergent terminal pathway of oxidative stress-autoimmunity-mediated melanocyte loss.

Tumor necrosis factor B (TNFB) genetic variants and its increased expression are associated with vitiligo susceptibility

Genetic polymorphisms in TNFB are involved in the regulation of its expression and are found to be associated with various autoimmune diseases. The aim of the present study was to determine whether TNFB +252A/G (rs909253) and exon 3 C/A (rs1041981) polymorphisms are associated with vitiligo susceptibility, and expression of TNFB and ICAM1 affects the disease onset and progression. We have earlier reported the role of TNFA in autoimmune pathogenesis of vitiligo, and we now show the involvement of TNFB in vitiligo pathogenesis. The two polymorphisms investigated in the TNFB were in strong linkage disequilibrium and significantly associated with vitiligo. TNFB and ICAM1 transcripts were significantly increased in patients compared to controls. Active vitiligo patients showed significant increase in TNFB transcripts compared to stable vitiligo. The genotype-phenotype analysis revealed that TNFB expression levels were higher in patients with GG and AA genotypes as compared to controls. Patients with the early age of onset and female patients showed higher TNFB and ICAM1 expression. Overall, our findings suggest that the increased TNFB transcript levels in vitiligo patients could result, at least in part, from variations at the genetic level which in turn leads to increased ICAM1 expression. For the first time, we show that TNFB +252A/G and exon 3 C/A polymorphisms are associated with vitiligo susceptibility and influence the TNFB and ICAM1 expression. Moreover, the study also emphasizes influence of TNFB and ICAM1 on the disease progression, onset and gender bias for developing vitiligo.

Repair efficiency and PUVA therapeutic response variation in patients with vitiligo

Vitiligo is an acquired depigmentation disorder affecting 0.1% to >8.8% in Indian population. Psoralen and ultraviolet A radiation (PUVA) is a gold standard treatment for vitiligo, however, response is still empirical. In order to investigate whether drug response variation is influenced by the repair ability of PUVA treated vitiligo subjects, single cell gel electrophoresis (SCGE) for genotoxicity and serum malonaldehyde (MDA) for cytotoxicity were performed on 107 subjects (77 cases and 30 healthy controls) in South Indian population. In vitro repair ability was assessed by considering the residual damage. A significant difference was observed between the patients and controls with regard to their mean values of DNA damage and MDA levels (p<0.05). On categorization to fast and slow responders based on the time of response, patients exhibited a significant deviation in residual DNA damage, suggestive of variation with respect to DNA repair efficiency (p<0.05). This is the first study to our knowledge with respect to PUVA drug response variation in vitiligo in relation to DNA repair. Large systematic studies on DNA repair may help in a better understanding of the mechanisms involved in the PUVA drug response variation.

Interleukin-4 genetic variants correlate with its transcript and protein levels in patients with vitiligo

BACKGROUND

Vitiligo is an acquired pigmentary disorder resulting from loss of melanocytes. Interleukin (IL)-4 has been shown to stimulate B-cell proliferation, to regulate immunoglobulin class switching (IgG1 and IgE) and to promote T-cell development. Polymorphisms in the IL4 gene are known to increase its expression, thereby implicating its role in vitiligo susceptibility.

OBJECTIVES

To explore intron 3 VNTR (IVS3) and -590 C/T (rs2243250) promoter polymorphisms in the IL4 gene and to correlate them with the IL4 transcript, serum IL-4 and IgE levels to achieve genotype-phenotype correlation in patients with vitiligo from Gujarat. A replication study was done in a North Indian population.

METHODS

The case-control study was performed to investigate these polymorphisms in 505 patients and 744 controls in Gujarat, and 596 patients and 397 controls in North India by polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism analysis. IL4 transcript levels were monitored by real-time PCR. Serum IL-4 and IgE levels were measured by enzyme-linked immunosorbent assay and electrochemiluminescence immunoassay, respectively.

RESULTS

The genotype frequencies differed significantly between patients with generalized vitiligo and controls for both the polymorphisms in both populations. Allele frequencies significantly differed between patients with generalized vitiligo and controls for both the polymorphisms in the population from Gujarat. Interestingly, genotype and allele frequencies for -590 C/T single nucleotide polymorphism were significantly different between patients with localized vitiligo and controls in both the populations. The study revealed significantly increased IL4 mRNA, serum IL-4 and IgE levels in patients from Gujarat. Age of onset analysis of disease in patients suggested that the TTR2R2, TTR1R2 and CTR2R2 haplotypes had a profound effect in the early onset of the disease.

CONCLUSIONS

Our results suggest that these polymorphisms of the IL4 gene may be genetic risk factors for susceptibility towards vitiligo and the upregulation of the IL4 transcript, protein and IgE levels in individuals with susceptible haplotypes reveal the crucial role of IL-4 in the pathogenesis of vitiligo.

Targeting skin: vitiligo and autoimmunity

In this issue, Singh and co-workers describe the results of classical typing of human leukocyte antigen (HLA) alleles in 1,404 vitiligo patients and 902 unaffected controls from North India and follow-up HLA typing in 355 cases and 441 controls from Gujarat. The increased frequency of DRB1*07:01 in North Indian and Gujarat populations with generalized and localized vitiligo and in several vitiligo populations studied previously suggests that it contributes to autoimmunity and destruction of melanocytes.

Vitiligo: a review of the published work

Vitiligo is a common depigmenting skin disorder, characterized by acquired, idiopathic, progressive, circumscribed hypomelanosis of the skin and hair, with total absence of melanocytes microscopically. It occurs worldwide, with an incidence rate of between 0.1% and 2%. Vitiligo is an important skin disease having a major impact on the quality of life of the patient suffering from it. The causes of this condition are uncertain but seem to be dependent on the interaction of genetic, immunological and neurological factors. Vitiligo coexists with other autoimmune disorders, Sutton or halo nevus, and malignant melanoma. The substantial disfigurement associated with vitiligo can cause serious emotional stress for the patient, which necessitates treatment. Because its pathogenesis is still not understood, there is a plethora of different treatments. Among them, topical steroids and narrowband ultraviolet B monotherapy were the most common as current treatments for localized and generalized vitiligo, respectively. Cosmetic improvement can be achieved by camouflage products and self-tanning dyes. The course of vitiligo is unpredictable, but often progressive. Spontaneous repigmentation may occur in a few people (10–20%), mainly in children, but this tends to be only partial and on sun-exposed areas. In this article, we review vitiligo as a whole, including epidemiology, pathogenesis and etiology, histopathology, clinical manifestations, classification, clinical variants, diagnosis and differential diagnoses, specific investigation, treatment, prognosis, psychosocial view and its association with other disorders.

ASSESSMENT OF MC1R AND α-MSH GENE SEQUENCES IN IRANIAN VITILIGO PATIENTS

Background:

Vitiligo is an acquired pigmentary disorder of the skin that is caused by unknown factors and is characterized by white and depigmented patches that enlarge and become more numerous with time. Genetic factors, oxidative stress, autoimmunity, and neurochemical agents, such as catecholamines might also contribute to vitiligo. Cutaneous pigmentation is determined by the amounts of eumelanin and pheomelanin synthesized by the epidermal melanocytes and interference of melanocortin-1 receptor (MC1R), a G-protein coupled receptor, its normal agonist, alpha-melanocyte stimulating hormone (α-MSH), and key enzymes, such as tyrosinase, to protect against sun-induced DNA damage. The MC1R, a 7 pass trans-membrane G-protein coupled receptor, is a key control point in melanogenesis. Loss-of-function mutations at the MC1R are associated with a switch from eumelanin to pheomelanin production, resulting in a red or yellow coat color.

Aim:

In this research, we aim to examine the genetic variety of MC1R and α-MSH gene in 20 Iranian vitiligo patients and 20 healthy controls.

Materials and Methods:

Analysis of the MC1R coding gene was performed with direct sequencing.

Results:

We found the following 9 MC1R coding region variants: Arg163Gl (G488A), Arg227Leu (G680A), Val 97Phe (G289T), Asp184Asn (G550A), Arg227Lys (G680A), Arg142His (G425A), Val60Leu (G178T), Val247Met (C739A), and Val174Ile (G520A). We also found 2 frameshift changes: one of them was the Insertion of C (frameshift in Pro136, stop at Trp148) and the other, Insertion of G (frameshift in Pro256, stop at Trp 333). Of all the changes, the most common was Val60Leu at 5% in patients vs 20% in controls, Val247Met at 15% in patients vs 0% in controls and Val174Ile at 15% in controls and 0% in patients. The other variants showed a frequency <5% in both patients and controls. Also in this study, we have examined the frequency of single nucleotide polymorphisms within the α-MSH genes with direct sequencing in 20 patients and 20 healthy subjects but found no changes along this gene.

Conclusion:

We could not find any relationship between MC1R and α-MSH genes and their effect on the disease in Iranian vitiligo patients.

Oxidative stress level and tyrosinase activity in vitiligo patients

Background:

Vitiligo is an acquired pigmentary disorder of the skin. Genetic factors, oxidative stress, autoimmunity, and neurochemical agents might be contributing factors for the development of the disease.

Aims:

To evaluate the oxidative stress level and tyrosinase activity in vitiligo patients and to compare them with healthy volunteers.

Materials and Methods:

We used Comet assay to evaluate DNA strand breaks in peripheral blood cells of active vitiligo patients. We then extracted total protein from lesional and nonlesional skin of ten selected patients. Tyrosinase activity was found to play a crucial role in melanogenesis.

Results:

The basal level of systemic oxidative DNA strand breaks in leukocytes increased in vitiligo patients compared to healthy participants. We observed that tyrosinase activity in lesional skin was lower than in nonlesional skin.

Conclusion:

Our finding suggests that increased levels of oxidative stress might impact tyrosinase activity and eumelanin synthesis via anabolism pathway of melanin synthesis. In sum, we observed a negative correlation between levels of systemic oxidative stress and of tyrosinase activity.

Vitiligo treatment with vitamins, minerals and polyphenol supplementation

BACKGROUND

Mammalian pigmentation results from the synthesis and accumulation of photo protective epidermal melanin. Melanin was formed from the amino acid precursor L-tyrosine within specialized cells, the melanocytes. Oxidative stress has been suggested to be the initial pathogenetic event in melanocyte degeneration with H(2)O(2) accumulation in the epidermis of patients with active disease. Auto immunity has been also suggested as another hypothesis in the pathogenesis of depigmentation disorders. Topical corticosteroids and phototherapy as common treatment modalities have been prescribed in patients with vitiligo. However, they are often not effective and safe (epidermal atrophy). Therefore, research for alternative therapies continues.

AIMS

To evaluate the beneficial effects of a supplementation with antioxidant vitamins (A, C, E) and minerals (zinc, selenium) for vitiligo treatment.

METHODS

Forty experimental autoimmune vitiligo mice C57BL6, aged from 5 to 12 months showing visible signs of induced vitiligo, were sequentially randomized into five parallel groups (8 mice per group). Each group mice was allocated an identical pre coded cage. the first group (SZV) received the ED + 1,4 g zinc (Zn) + 0.04 g selenium (Se) + vitamins (A 118 UI, C 8,5 mg, E 5,4 UI) /kg diet, the second group (PSZV) received the ED + 1,4 g zinc (Zn) + 0.04 g selenium (Se) + vitamins (A 118 UI, C 8.5 mg, E 5,4 UI)/kg diet + Polyphenol orally, the group 3 (PSZ) received the ED + green tea decoction prepared from 100 g/l (polyphenol orally) + 1,4 g Zn + 0.04 g Se, the 4 (P) received the ED + green tea decoction prepared green tea decoction prepared from 100 g/l, the control group 5(C) received the ED + distilled water. Cure was defined as repigmentation of treated sites. Photographic and optical techniques were used both at the baseline and on weekly basis.

RESULTS

By the end of the study, mice showed visible repigmentation. Using the investigator's global assessment, therapeutic success in terms of a clear repigmentation documented in 70% of treated mice.

CONCLUSION

Our findings suggest that an antioxidant supplementation is significantly beneficial in contributing superior clinical efficacy to cure vitiligo.

Intraepidermal injection of dissociated epidermal cell suspension improves vitiligo

This study was initiated to evaluate the safety and effectiveness of intraepidermal injection of dissociated epidermal cells into the lesions of stable vitiligo patients. Autologous dissociated epidermal cell suspensions were injected intraepidermally into 10 stable vitiligo patients. None of the patients received adjuvant therapy. The response was evaluated as: marked (76-100%), moderate (51-75%), mild (26-50%) and minimal repigmentation (0-25%). Transmission electron microscopy was used to evaluate the transplanted cells and immunohistochemical staining with HMB-45 was performed to assess the repigmentation in vivo. In all cases, repigmentation started during the 4-week period after transplantation. Six months after transplantation, a marked repigmentation in four (40%), moderate repigmentation in two (20%) and mild repigmentation in two (20%) patients were observed. Two (20%) patients with white patches on their lids showed minimal repigmentation. No side effects were observed in any patients. Interestingly, repigmentation of gray hair in one patient, 4 months post transplantation was observed. Analysis of the ultrastructure of transplanted cells showed 1.5% of the cells had melanocyte morphology. HMB-45 positive cells were observed after cell transplantation. This method is an effective, simple and safe therapeutic option for stable vitiligo lesions.

The Double Strike Hypothesis of the vitiligo pathomechanism: new approaches to vitiligo and melanoma

Based on current research, we present a consolidated set of theses which explain the pathomechanisms of vitiligo- and melanoma-associated hypopigmentation. The main thesis is the Double Strike Hypothesis, i.e. vitiligo is caused by at least two different major pathomechanisms: an antibody-based pathomechanism and a T-cell-based pathomechanism. The antibody-based pathomechanism is dominant in diffuse vitiligo, while the T-cell based pathomechanism is dominant in localised vitiligo. Based on this main thesis we derive new therapeutical approaches to vitiligo and melanoma by using the different pathomechanisms. Finally we explain why melanoma-associated hypopigmentation as a natural immunotherapy is still in statu nascendi.

A functional single-nucleotide polymorphism in the catechol-O-methyltransferase gene alter vitiligo risk in a Chinese population

Vitiligo is an acquired hypomelanotic skin disorder resulting from the loss of functional melanocytes. The COMT-158 polymorphism can reduce COMT enzyme activity and may thus lead to the overproduction of toxic radicals in the melanocyte microenvironment. To determine whether this polymorphism in the COMT gene is associated with an increased risk of vitiligo in Chinese populations, we used a polymerase chain reaction sequence-specific primer (PCR-SSP) technique to determine the frequency of the polymorphism COMT-158 G > A in 749 vitiligo patients and 763 healthy controls. We found that compared to the COMT-158 GG genotype, the COMT-158 GA genotype (adjusted odds ratio [OR], 1.39; 95% confidence interval [CI], 1.13-1.72) and the combined GA + AA genotype (adjusted OR, 1.41; 95% CI, 1.15-1.74) were associated with an increased risk of generalized vitiligo. The association was more pronounced in patients with early-onset vitiligo (adjusted OR, 1.95; 95% CI, 1.45-2.60), those with a family history of vitiligo (adjusted OR, 3.84; 95% CI, 2.47-5.96), and female patients (adjusted OR, 1.74; 95% CI, 1.29-2.36). When we further clinically stratified the vitiligo patients according to their disease types, we found that the combined GA + AA genotype was associated with vitiligo vulgaris (adjusted OR, 1.31; 95% CI, 1.02-1.68), focal vitiligo (adjusted OR, 1.62; 95% CI, 1.17-2.25), and universal vitiligo (adjusted OR, 1.50; 95% CI, 0.98-2.30), but not with acrofacial vitiligo (adjusted OR, 1.53; 95% CI, 0.86-2.73) or segmental vitiligo (adjusted OR, 1.35; 95% CI, 0.72-2.51). In conclusion, this COMT gene polymorphism may have contributed to the etiology of vitiligo in our Chinese population. Larger population-based studies are required to verify our findings.

The Ca2+-binding capacity of epidermal furin is disrupted by H2O2-mediated oxidation in vitiligo

The Ca(2+)-dependent precursor convertase furin is abundantly expressed in epidermal keratinocytes and melanocytes. In this context, it is noteworthy that proopiomelanocortin (POMC) cleavage is also processed by furin, leading to ACTH, beta-lipotropin, and beta-endorphin. All prohormone convertases including furin are regulated by Ca(2+). Because numerous epidermal peptides and enzymes are affected by H(2)O(2)-mediated oxidation, including the POMC-derived peptides alpha-MSH and beta-endorphin as shown in the epidermis of patients with vitiligo, we here asked the question of whether furin could also be a possible target for this oxidation mechanism by using immunofluorescence, RT-PCR, Western blotting, Ca(2+)-binding studies, and computer modeling. Our results demonstrate significantly decreased in situ immunoreactivity of furin in the epidermis of patients with progressive vitiligo (n = 10), suggesting H(2)O(2)-mediated oxidation. This was confirmed by (45)Ca(2+)-binding studies with human recombinant furin identifying the loss of one Ca(2+)-binding site from the enzyme after oxidation with H(2)O(2). Computer simulation supported alteration of one of the two Ca(2+)-binding sites on furin. Taken together, our results implicate that the Ca(2+)-dependent proteolytic activity of this convertase is targeted by H(2)O(2), which in turn could contribute to the reduced epidermal expression of the POMC-derived peptides alpha-MSH and beta-endorphin as documented earlier in patients with vitiligo.

Percutaneous penetration, melanin activation and toxicity evaluation of a phytotherapic formulation for vitiligo therapeutic

The aim of this work was to apply photoacoustic spectroscopy for the ex vivo determination of the penetration rate of a phytotherapic formulation for vitiligo therapeutic, with or without salicylic acid as the promoter agent. In addition, the compound toxicity and morphophysiology effects were evaluated for different concentrations of salicylic acid. The experiments were performed as a function of the period of time of treatment in a well-controlled group of rabbits. Toxic effects were not observed with any of the tested products. All formulations containing salicylic acid induced cutaneous reaction which was dose dependent. The histological analysis showed that the use of the medication was associated with an increased comedogenic effect in relation to the control group, regardless of salicylic acid concentration. Inflammatory reactions and acanthosis were observed only in the animals treated with formulations containing higher concentrations of salicylic acid, while none of these effects were detected with the use of the formulation containing 2.5% (wt/vol) of salicylic acid. Photoacoustic depth monitoring showed that both formulations, with or without salicylic acid, propagated through the skin up to the melanocytes region, suggesting that the transport of the active agent may occur through the epithelial structure without the need of using queratinolitic substances, which are known to induce side effects in the animals.

Rosmarinic acid induces melanogenesis through protein kinase A activation signaling

Melanogenesis is a physiological process that results in the synthesis of melanin pigments, which play a crucial protective role against skin photocarcinogenesis. In order to determine the effects of rosmarinic acid on melanogenesis and elucidate the molecular events of melanogenesis induced by rosmarinic acid, several experiments were performed in B16 melanoma cells. In this study, we showed that the melanin content and tyrosinase expression were increased by rosmarinic acid in a concentration-dependent manner. In addition, after the melanin content was increased by rosmarinic acid, it was reduced by H-89 and KT 5720, protein kinase A (PKA) inhibitors, but not by SB203580, a p38(mapk) inhibitor, or Ro-32-0432, a PKC inhibitor, which suggests the involvement of PKA in rosmarinic acid-induced melanogenesis. Consistent with this, rosmarinic acid induced the phosphorylation of CRE-binding protein (CREB), but had no effect on the phosphorylation of p38(mapk) or the inhibition of Akt phosphorylation. Additionally, rosmarinic acid induced the activation of cAMP response element (CRE) without having any effect on cAMP production, which suggests that rosmarinic acid-induced melanogenesis is mediated by PKA, which occurs downstream of cAMP production. This result was further confirmed by the fact that rosmarinic acid-induced phosphorylation of CREB was inhibited by H-89, but not by PD98059, a MEK1 inhibitor, or by LY294002, a phosphatidylinositol-3-kinase (PI3K) inhibitor. Rosmarinic acid-induced expression of tyrosinase protein was attenuated by H-89. Based on these results, we report for the first time that rosmarinic acid induces melanogenesis through PKA activation signaling.

Association of HLA loci alleles and antigens in Saudi patients with vitiligo

HLA complex is composed of several closely linked loci, each containing several alleles, yielding a high expression of polymorphism. Vitiligo, a commonly acquired dermatological disorder, has been associated with different HLA antigens in different ethnic groups. In this study, HLA classes I (HLA-A, B, and C) and II (HLA-DR, DQ) antigens/alleles were analyzed in a group of 80 Saudi subjects consisting of vitiligo patients (40) and matched controls (40). The frequency of antigens of various HLA loci was tested using two-stage microcytotoxicity assays, while the frequency of alleles of HLA-DR was screened by polymerase chain reaction/sequence specific primers (PCR/SSP) method. The frequencies of HLA-B7, B15, Bw6, Cw6, Cw7, and DRB4*010101 were found to be significantly higher in vitiligo patients compared to controls [P = 0.029, 0.015, 0.033, 0.009, 0.043, and 0.015, respectively, with relative risk (RR) > or = 3, etiologic fraction (EF) > or = 0.4]. On the other hand, HLA-A9, B5, DQ1, and DRB3*010101 were significantly decreased in vitiligo patients compared to healthy Saudis [P = 0.008, 0.004, 0.028, and 0.04, respectively, with RR < 1 and preventive fraction (PF) < 0.5]. Among the patients, the highest allele frequency was noted for DRB4*010101(70%), while in controls it was for DRB3*010101 (72.5%). These results for antigens and allele frequency of various HLA Loci in vitiligo patients and control subjects suggested that HLA-B7, Bw6, Cw6, Cw7, and DRB4*010101 could be susceptible to vitiligo, while HLA-A9, B5, DQ1, and DRB3*010101 might be negatively associated with the development of vitiligo in Saudis.

Dopamine-induced apoptosis in human melanocytes involves generation of reactive oxygen species

BACKGROUND

Previous studies have shown that significant increases in urinary and plasma levels of several monoamines and their metabolites characterize the onset of vitiligo and its progression. Recently, both epidermal keratinocytes and melanocytes were found to have the capacity for the biosynthesis of several catecholamines and serotonin. Some monoamines and their metabolites can induce apoptosis and cytotoxicity in neural cells. However, no previous report has investigated the potential role of these monoamines in inducing apoptosis or cytotoxicity in melanocytes.

OBJECTIVES

To study the effects of dopamine (DA), norepinephrine (NE), epinephrine (EP), and serotonin (5-HT) on melanocyte cytotoxicity and apoptosis.

METHODS

Primary cultures of normal human melanocytes established from the foreskins of normal individuals were treated with different concentrations of DA, NE, EP and 5-HT for 5 and 7 days. Cell viability was measured by the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Melanocyte apoptosis was evaluated by morphological examination and flow cytometric analysis. We also measured the generation of reactive oxygen species (ROS) after DA treatment.

RESULTS

Among the four monoamines used in this study, only DA had an effect, dose-dependently decreasing the melanocyte viability at concentrations ranging from 0.01 to 100 micromol L(-1) (0.1 and 1 micromol L(-1), P < 0.05; 10 micromol L(-1), P < 0.01). In addition, DA-induced melanocyte apoptosis was evidenced by the increased percentage of sub-G1 cells from 7.71 +/- 0.28% (control) to 12.22 +/- 1.05% (0.1 micromol L(-1) DA) (P < 0.005), and treatment with the antioxidant N-acetylcysteine (NAC) reversed this apoptotic effect. DA treatment led to the generation of ROS, which could be prevented by pretreatment with NAC.

CONCLUSIONS

DA can induce melanocyte apoptosis, which might be related to the generation of ROS. This novel effect might play an important role in the development or progression of vitiligo, which is currently viewed as a disease process closely related to melanocyte apoptosis.

Estrogens can contribute to hydrogen peroxide generation and quinone-mediated DNA damage in peripheral blood lymphocytes from patients with vitiligo

To date there is ample in vivo and in vitro evidence for increased epidermal and systemic hydrogen peroxide (H(2)O(2)) levels in vitiligo, which can be reduced with a topical application of a pseudocatalase-K.U. Schallreuter (PC-KUS) leading to the recovery of epidermal catalase levels as well as other enzymes in peripheral blood cells. Recently, the generation of H(2)O(2) by oxidative metabolism of estrogens and other aromatic steroids was documented. Therefore, it was tempting to follow estrogen-generated H(2)O(2) and its possible effect on DNA damage in peripheral blood lymphocytes from patients with vitiligo before and after the reduction of epidermal H(2)O(2) with pseudocatalase PC-KUS compared to controls. For this purpose, 20 Caucasian patients were grouped in treated responders (group A, n=11) and untreated active/acute disease (group B, n=9) and compared to Caucasian healthy controls (group C, n=7). Consequently, epidermal catalase protein expression in full skin biopsies was assessed using immunofluorescence labelling together with determination of basal H(2)O(2) levels in peripheral blood lymphocytes. To test the influence of estrogen on H(2)O(2) generation and DNA damage, freshly prepared peripheral blood lymphocytes from all three groups were used for the alkaline comet assay in the presence and absence of catalase. The results of this study demonstrated that reduction of epidermal H(2)O(2) leads to both increased epidermal catalase protein expression as well as decreased H(2)O(2) concentrations in lymphocytes. Moreover, a direct estrogen-mediated DNA damage was identified in both patient groups, which was absent in healthy controls. This effect was not abolished by catalase pointing to direct quinone-mediated DNA damage by estrogens in peripheral blood lymphocytes in vitiligo.