Chemical leukoderma: An insight of pathophysiology and contributing factors.

Chemical leukoderma, or chemical-based vitiligo, is a dermal disease triggered by exposure to chemicals and characterized by the emergence of depigmentation or hypopigmentation of the skin. The etiology of this condition is associated with exposure to various chemical substances present in both occupational and non-occupational settings. The precise mechanism that underlies chemical leukoderma remains elusive and is believed to result from the demise of melanocytes, which are responsible for producing skin pigments. This condition has gained particular prominence in developing countries like India. An interesting connection between chemical leukoderma and vitiligo has been identified; studies suggest that exposure to many household chemicals, which are derivatives of phenols and catechol, may serve as a primary etiological factor for the condition. Similar to autoimmune diseases, its pathogenesis involves contributions from both genetic and environmental factors. Furthermore, over the last few decades, various studies have demonstrated that exposure to chemicals plays a crucial role in initiating and progressing chemical leukoderma, including cases stemming from occupational exposure.

Integrating neuronal involvement into the immune and genetic paradigm of vitiligo.

In this review we show how the neuronal theory is relevant to the convergence theory for the mechanism causing vitiligo, especially the segmental type. Neuropeptides and neurotransmitters, such as neuropeptide Y and dopamine, can be central to the pathological mechanisms of melanocyte destruction. They link into a bidirectional network connecting cutaneous nerves, the neuroendocrine axis and the immune system, and through their local influence on cutaneous inflammation, to the antigen-specific regulatory T cells and the chemokine ligand type 9/chemokine receptor type 1 axis, which is thought to be the final pathway for melanocyte destruction.

PINK1 in normal human melanocytes: first identification and its effects on H2 O2 -induced oxidative damage.

BACKGROUND: Oxidative stress plays an important role in initiating the destruction of melanocytes, which could be one possible mechanism of vitiligo. PINK1 is an outer membrane protein of mitochondria, which protects many cells from oxidative stress through regulating mitochondrial function. However, the role of PINK1 and its effects on oxidative damage in melanocytes have not been elucidated. AIM: To investigate the expression and effects of PINK1 on oxidative stress in human melanocytes. METHODS: Quantitative reverse transcription-PCR and western blot analysis were used to analyse the expression of PINK1 in PIG1 melanocyte and gene downregulation models. Levels of cell viability, cell apoptosis and intracellular reactive oxygen species (ROS), mitochondrial morphology, mitochondrial membrane potential (MMP) and mitochondrial permeability transition pore (MPTP) opening were measured in PIG1 models transfected with PINK1 small interfering RNA with or without hydrogen peroxide (H2 O2 ). RESULTS: We first observed the expression of PINK1 in human PIG1 melanocytes and found that downregulation of PINK1 made melanocytes more sensitive to oxidative stress induced by H2 O2 , with more cell apoptosis and increased intracellular ROS. Meanwhile, downregulation of PINK1 caused morphological changes in mitochondria, decreased the MMP and increased MPTP opening. CONCLUSIONS: Our study found PINK1 plays an essential role in protecting human melanocytes from oxidative stress.

H2 O2 -induced oxidative stress disrupts mitochondrial functions and impairs migratory potential of human epidermal melanocytes.

Reactive oxygen species (ROS) have already been demonstrated to impede the migratory ability in non-melanocytic cell lines by depleting mitochondrial ATP production. Therefore, understanding the mitochondrial metabolic response to migration in the presence of ROS should be a key to understanding repigmentation in vitiligo. This study aimed to investigate the energy mechanism associated with the ROS-mediated attenuation of melanocyte migration. After melanocytes were pretreated with H2 O2 , their ATP production, migratory ability, ultrastructural changes and Mitochondrial Permeability Potential were analysed. The results showed that, in parallel with the decreased ATP production, the migratory ability of melanocytes was significantly inhibited by oxidative stress. Supplementation with exogenous ATP reversed the suppressed ATP-dependent migration of melanocytes. Melanocytes were then stressed with H2 O2 and Agilent Whole Human Genome microarray analysis identified 763 up-regulated mRNAs and 1117 down-regulated mRNAs. Among them, 11 of the encoded proteins were involved in mitochondrial ATP production and their expression levels were verified. The decreased expression of NADH dehydrogenase 2(ND2) , cytochrome c oxidase 1(COX1) and cytochrome c oxidase 3(COX3) was shown to be involved in the depletion of mitochondrial ATP production, which was coupled with the impaired migratory potential. These results indicate that the migration of melanocytes relies heavily on an inexhaustible supply of ATP from mitochondria.

Lesional skin in vitiligo exhibits delayed in vivo reepithelialization compared to the nonlesional skin.

Vitiligo, a common skin disorder, is characterized by the loss of functional melanocytes resulting in the depigmentation of skin. Previous studies have demonstrated molecular and architectural alterations in the epidermal keratinocytes upon loss of melanocytes. The physiological implications of these "altered" keratinocytes are yet not known. We investigated the wound healing efficiency of lesional vs nonlesional skin in 12 subjects with stable nonsegmental vitiligo using histological and ultrastructural evaluation of partial-thickness wounds. The wounds were examined 12 days postinjury, coinciding with the reepithelialization phase of healing marked primarily by keratinocyte migration and proliferation. This study demonstrated a significant difference in the reepithelialization potential between the lesional and nonlesional skin. While all 12 nonlesional wounds demonstrated considerable neoepidermis formation on the 12th day post wound, only four of the corresponding lesional samples showed comparable reepithelialization; the rest remaining in the inflammatory phase. Ultrastructural studies using transmission electron microscopy as well as immunohistochemical staining revealed a reduced number of desmosomes, shorter keratin tonofilaments and an increase in myofibroblast population in the dermis of lesional reepithelialized tissue compared to the nonlesional reepithelialized samples. This study implicates gross functional perturbations in the lesional skin during physiological wound healing in vitiligo, suggesting that the breakdown of keratinocyte-melanocyte network results in delayed wound repair kinetics in the lesional skin when compared to patient-matched nonlesional skin.

Current insight into the roles of microRNA in vitiligo.

Vitiligo is a common chronic depigmented skin disease characterized by melanocyte loss or dysfunction in the lesion. The pathogenesis of vitiligo has not been fully clarified. Most studies have suggested that the occurrence and progression of vitiligo are due to multiple factors and gene interactions in which noncoding RNAs contribute to an individual's susceptibility to vitiligo. Noncoding RNAs, including microRNAs (miRNAs), are a hot topic in posttranscriptional regulatory mechanism research. miRNAs are noncoding RNAs with a length of approximately 22 nucleotides and play a negative regulatory role by binding to the 3'-UTR or 5'-UTR of the target mRNA to inhibit translation or initiate mRNA degradation. Previous studies have screened the differential expression profiles of miRNAs in the skin lesions, melanocytes, peripheral blood mononuclear cells (PBMCs) and sera of patients and mouse models with vitiligo. Moreover, several studies have focused on miRNA-25, miRNA-155 and other miRNAs involved in melanin metabolism, oxidative stress, and melanocyte proliferation and apoptosis. These miRNAs and regulatory processes further illuminate the pathogenesis of vitiligo and provide hope for the application of small molecules in the treatment of vitiligo. In this review, we summarize miRNA expression profiles in different tissues of vitiligo patients and the mechanisms by which key miRNAs mediate vitiligo development.

Controversial issues in vitiligo patients: a review of old and recent treatments.

Vitiligo is quite a common hypopigmentary disorder, which may affect both children and adults with important psychological effects due to the well-known leopard skin-like appearance. The authors summarize in the present study the published evidence on vitiligo with particular interest on the controversial aspects of the disease, such as its definition and the available treatments.

A preliminary study of fractional CO2 laser added to topical tacrolimus combined with 308 nm excimer lamp for refractory vitiligo.

Fractional CO2 laser has been proposed recently to be effective and well tolerated in patients with refractory vitiligo. In this preliminary, prospective study, 21 patients with multiple, localized, refractory, non-segmental vitiligo lesions were randomized to receive either tacrolimus ointment plus 308 nm excimer lamp (control), with or without the addition of fractional CO2 laser. There was no statistically significant improvement in the repigmentation on the laser side compared to the control side. Treatment was generally well-tolerated; only localized adverse effects were noted. Overall the triple combination therapy was not superior to tacrolimus ointment plus 308 nm excimer lamp. Treatment failure may reflect insufficient penetration of tacrolimus ointment through the holes created by fractional CO2 laser on the skin.

Clinical and Spectrophotometric Evaluation of Skin Photoadaptation in Vitiligo Patients after a Short Cycle of NB-UVB Phototherapy.

BACKGROUND: The phenomenon of photoadaptation to narrow-band ultraviolet B (NB-UVB) radiation has been previously described in vitiligo and has usually been clinically measured by the assessment of the minimal erythema dose (MED) after phototesting. OBJECTIVES: To assess the photoadaptive response in vitiligo and healthy skin after NB-UVB phototherapy not only clinically, but also by spectrophotometry. MATERIALS AND METHODS: Fourteen patients affected by generalized vitiligo underwent NB-UVB phototherapy twice weekly for 12 weeks. Before and after phototherapy, a phototesting procedure was administered on vitiligo patches and adjacent healthy skin with a solar simulated radiation (SSR). Visual assessment of the MED took place after 24 h. A spectrophotometer was used to assess the a* value and the melanin index (MI*), as signs of skin erythema and pigmentation. The photoadaptation factor (MED-PF) and the a* photoadaptation factor (a*-PF) were calculated. RESULTS: After NB-UVB phototherapy, both vitiligo and healthy skin showed an increase in MED and MI* values and a reduction of skin erythema compared to baseline (p < 0.05). MED-PF data showed a photoadaptation in 10 (71.4%) vitiligo lesions and in 12 (85.7%) healthy skin areas. The assessment of the a*-PF showed a negative mean percentage value in all affected and unaffected skin areas. CONCLUSIONS: A short cycle of NB-UVB phototherapy can induce photoadaptation in vitiligo by increasing the MED and reducing skin erythema after stimulation with SSR. This is most likely due to the physical filter function induced by ultraviolet radiation.

Is the +405 G/C single nucleotide polymorphism of the vascular endothelial growth factor (VEGF) gene associated with late-onset vitiligo?

The increasing body of evidence for the relationship between the vascular endothelial growth factor (VEGF) polymorphism and autoimmune disorders combined with the enhanced expression of this angiogenic factor in vitiligo makes VEGF a very interesting candidate gene to be investigated in vitiligo. The aim of this study was to evaluate the possible associations between the +405 G/C single nucleotide polymorphisms (SNP) of the VEGF gene (rs2010963) and vitiligo. The independent case-control population sample of 152 patients with vitiligo and 152 matched controls was evaluated in this study. A questionnaire was completed for each vitiligo patient to document the demographic and clinical characteristics of the patients. All enrolled individuals had a venous blood sample collected. Genotype frequencies for +405 G/C VEGF gene polymorphism were determined using polymerase chain reaction (PCR) amplification and restriction fragment length polymorphism (RFLP) analysis. There were no significant differences in genotype or allele distributions for this SNP between cases and controls. However, we observed a significant association between GG genotype and higher age at onset of vitiligo (p = 0.04). Moreover, patients stratification revealed a significant increase in the frequency of GG genotype compared to CC + CG genotypes in patients with the late onset (≥20 years) vitiligo (p = 0.05). Although these results are not conclusive, they could potentially lead to considering the angiogenic factors as a potential target for therapy in late-onset vitiligo.

Perspectives of New Advances in the Pathogenesis of Vitiligo: From Oxidative Stress to Autoimmunity.

Vitiligo is an autoimmune cutaneous disease in which melanocytes are destroyed by CD8⁺ T cells resulting in disfiguring white spots. From the very beginning of the disease, oxidative stress plays a significant role in promoting the onset of vitiligo, as noted by many studies. Multiple factors lead to the overproduction of reactive oxygen species (ROS), and collaboratively cause ROS accumulation in vulnerable melanocytes. However, ROS are responsible for melanocyte damage manifested by the level of molecules, organelles, and cells, and the generation of autoantigens, through different pathways related to the dysregulation of melanocytes. Recent studies have shown that presentation of autoantigens is mediated by innate immunity, which bridges the gap between oxidative stress and adaptive immunity. The recruitment of CD8⁺ T cells induced by cytokines and chemokines guarantees the final destruction of epidermal melanocytes. Moreover, emerging concerns regarding regulatory T cells and resident memory T cells help explain the reinstatement and relapse of vitiligo. Here, we provide new perspectives in the advances in understanding of this disease pathogenesis and we attempt to find more interrelationships between oxidative stress and autoimmunity.

The Use of Janus Kinase Inhibitors in Vitiligo: A Review of the Literature.

Vitiligo is a common acquired depigmenting disorder characterized by the development of white macules and patches due to the loss of melanocytes. Patients with vitiligo can be stigmatized by society, making the disease a source of psychological stress that can considerably affect quality of life. The goal of vitiligo treatment is to obtain skin repigmentation in the majority of cases, and less commonly to depigment the remaining normal skin. There is no consistent, long-term, durable therapy for vitiligo for all patients, highlighting the unmet need for new safe and effective therapies to control this disease. Recently, JAK inhibitors have been explored as a promising novel treatment option in vitiligo. The JAK and signal transducers and activators of transcription (STAT) pathway is an attractive therapeutic target because IFN-γ-dependent cytokines produced through this pathway have been implicated in the pathogenesis of disease. This literature review describes vitiligo pathophysiology, explains the usefulness of the JAK inhibitors for treatment, and summarizes published case reports, case series, and open-label studies. Research outlined here shows JAK inhibitors in patients with vitiligo have a favorable safety profile and effectively produce repigmentation of lesions, especially with concomitant ultraviolet exposure. Additional studies are required to confirm efficacy, establish safety, and investigate durability of repigmentation.

An In-Vitro Assay Estimating Changes in Melanin Content of Melanoma Cells due to Ultra-Dilute, Potentized Preparations.

INTRODUCTION: The authors had previously conducted an in-vitro study to observe the effect of homeopathic medicines on melanogenesis, demonstrating anti-vitiligo potential by increasing the melanin content in murine B16F10 melanoma cells. A similar experiment was performed using further homeopathic preparations sourced from kojic acid (KA), hydrogen peroxide (H2O2; HP), 6-biopterin (BP), and [Nle4, D-Phe7]-α-melanocyte-stimulating hormone (NLE), some of which are known to induce vitiligo or melano-destruction at physiological dose. MATERIALS AND METHODS: The homeopathic preparations of BP, KA, NLE, and HP were used in 30c potency. Alcohol and potentized alcohol were used as vehicle controls. Prior to starting the main experiment, the viability of B16F10 melanoma cells after treatment with study preparations was assayed. Melanin content (at 48 h and 96 h) and tyrosinase activity in melanocytes were determined. RESULTS: At the end of 48 hours, NLE and HP in 30c potency had a significantly greater melanin content (p = 0.015 and p = 0.039, respectively) compared with controls; BP and KA in 30c potency had no significant effects. No significant changes were seen at the end of 96 hours. KA, NLE, HP, and vehicle controls showed an inhibition of tyrosinase activity. CONCLUSION: The study demonstrated melanogenic effects of two homeopathic preparations. Further research to evaluate the therapeutic efficacy of these medicines is warranted.

Response of localized, resistant, tingling vitiligo to pregabalin: A case report.

Vitiligo is a common depigmenting disease with complex pathogenesis. One of the proposed pathogenesis is the neural hypothesis, which suggests an altered reaction to neuropeptides, catecholamines, and their metabolites affecting melanocytes. Here, we report a case of 26-year-old female patient, whose vitiligo patches were associated with unusual crawling and tingling sensation and responded to a clinical trial of pregabalin.

Fractional Carbon Dioxide Laser as an "Add-on" Treatment for Vitiligo: A Meta-analysis with Systematic Review.

Treatment of vitiligo is challenging and requires a multidisciplinary approach. Fractional carbon dioxide (CO2) laser as an add-on to conventional treatment has been reported to be effective, but there is no consensus on its use. A systematic review was performed by searching major databases for relevant publications to February 2017. Six studies with 85 participants were included. For those with refractory vitiligo, the addition of fractional CO2 laser to routine treatment modalities was superior to conventional treatment alone in terms of > 50% re-pigmentation (risk ratio (RR) 4.90, 95% confidence interval (95% CI), 1.15-20.93; p = 0.03), physician improvement score (mean difference (MD) 0.81, 95% CI 0.33-1.29; p < 0.001), < 25% re-pigmentation (RR 0.64, 95% CI, 0.49-0.85; p=0.002) and patient satisfaction (MD 1.61, 95% CI 0.73-2.49; p< 0.001). Side-effects were minor. These results provide evidence supporting that fractional CO2 laser is a valuable treatment modality for patients with vitiligo, especially for those with refractory vitiligo.

Predictive Model for Response Rate to Narrowband Ultraviolet B Phototherapy in Vitiligo: A Retrospective Cohort Study of 579 Patients.

Vitiligo is an acquired depigmenting disorder. To date, there is no predictive model for its response rate to narrowband ultraviolet B (NBUVB) phototherapy. The aim of this study was to investigate the different types of response of patients with non-segmental vitiligo undergoing NBUVB 3 times a week. Many patients who were previously considered non-responders were given the opportunity to continue the treatment. Long-term maintenance of treatment and follow-up of a cohort of 579 patients enabled different subtypes of response (very rapid, rapid, average, slow and "non-responders") to be described for the first time, and a predictive model of response to be constructed based on repigmentation rate in the first 48 sessions of NBUVB. Among those patients who did not respond during the first 48 sessions, a new subgroup of patients was found, termed "very-slow" responders, who achieved a low, but significant, level of repigmentation after 96 sessions of NBUVB.

The assessment of macular electrophysiology and macular morphology in patients with vitiligo.

PURPOSE: We aimed to analyze the electrophysiologic function and morphology of macula in vitiligo patients. METHODS: Seventeen patients with vitiligo and 11 healthy subjects were studied. All participants underwent multifocal electroretinography (mfERG) and spectral domain optical coherence tomography (SD-OCT) evaluations. The mfERG (P1 mfERG responses central and peripheral) and retinal layer segmentation parameters (nine ETDRS subfields) were compared in vitiligo and control groups. RESULTS: The mean P1 response amplitudes were significantly decreased in central and peripheral rings of the fovea in patients with vitiligo compared with controls (p = 0.002 and p = 0.006, respectively). There was a tendency toward a prolonged mean implicit time for both central and peripheral in patients with vitiligo compared to controls, however, with no statistical significance (p = 0.453 and p = 0.05, respectively). There was no statistically significant difference in all retinal layers thickness between two groups. CONCLUSION: In patients with vitiligo, while photoreceptor segment preserved in SD-OCT, mfERG reduced showing potential decline in central retinal function. This study showed a potential decline in central retinal function in patients with vitiligo even if they have normal fundus appearance and SD-OCT findings.

Involvement of Different Genes Expressions during Immunological and Inflammatory Responses in Vitiligo.

Vitiligo is a condition of the skin distinguished by hypo-pigmentation. Etiology of this disorder is unknown, and several theories and mechanisms have been hypothesized. The inflammatory response in vitiligo is thought to be mediated by polymorphism in genes such as FOXP3, ACE, APE, GSTP1, TLR, SOD, CTLA-4, TAP/LMP gene cluster, etc. Theories including reactive oxygen species model, Nrf2-antioxidant response element (ARE) pathway, WNT pathway, tyrosinase activity, biochemical, molecular, and cellular alterations have been hypothesized to explain vitiligo pathogenesis. Melanosomal proteins are involved in antigen processing. The antigens are expressed to the T-cells in the form of peptides with HLA class II molecules. T-cells are activated in response to the discharge of co-stimulatory molecules such as LFA-3 as well as ICAM-1. An adaptive immune response is thus elicited, and the melanocytes eventually die or start malfunctioning and the skin undergoes hypo-pigmentation. IFN-γ is known to be a melanocyte inhibitor of paracrine origin; it is clearly involved in the early onset of symptoms of vitiligo disease. The surge in the IFN-γ levels mediates augmented expression of ICAM-1 molecule on the melanocytes, thereby establishing cytokine-mediated destruction of melanocytes. Mainly, mediators released by melanocytes and the functionality of keratinocytes decrease the disease activity. Such mediators include ET-1 as well as SCF, increase the pigmentation particularly when a patient is given with the UVB treatment. By scavenging ROS and screening UV radiation, melanin limits the damage caused to the cutaneous cells by UV radiation. Various immune responses play important roles in vitiligo.

Simultaneous improvement and worsening of vitiligo lesions during the course of NB-UVB phototherapy; vitiligo may not act as one unit.

Re-pigmentation and stabilization are the two ultimate goals of any re-pigmenting plan designed for vitiligo management. Furthermore, whether the improvement of some vitiligo lesions could be considered a guarantee for a similar response and/or stabilization of the rest of the lesions or not, remains to be clarified. To evaluate the behavior of non-segmental vitiligo (NSV), while on narrow band-ultraviolet B (NB-UVB) phototherapy. 25 patients with stable generalized NSV were included and received NB-UVB twice weekly. For the sake of ensuring accuracy of follow up, up to four lesions were randomly chosen in each patient and regularly measured using the point counting technique. The over-all point counting technique of all included patients showed a significant reduction (18.5 ± 8.4 cm2 to 8.2± 3.1 cm2 ) after 6 months of therapy (p < .001). Nine patients (36%), showed mixed response in the different lesions. Improvement was documented in some lesions, while other lesions showed no response or even worsening. No significant correlations were detected between the behavior of vitiligo during NB-UVB and any of the demographic or clinical data of the patients. NB-UVB is a pillar in the management of vitiligo, however close follow-up of the patient as a whole and his lesions, by both subjective and objective measures are mandatory to detect activity as early as possible, as vitiligo at many times may not act as one unit. This early detection of activity and the subsequent change in the treatment policy may ultimately change the final outcome of treatment.

New approach in the treatment of refractory vitiligo: CO2 laser combined with betamethasone and salicylic acid solution.

The aim of this study is to evaluate the use of fractional carbon dioxide laser (CO2 ) with betamethasone and salicylic acid solution in the treatment of patients with refractory vitiligo in hands. Each hand of the patient was randomly assigned to one of two groups: lesion treated with fractional carbon dioxide laser associated with betamethasone and salicylic acid solution administration or lesion treated only with betamethasone and salicylic acid solution. We conclude that combined treatment with fractional carbon dioxide laser and betamethasone associated with salicylic acid solution could effectively and safely be used in the treatment of refractory vitiligo.