Association of interferon-gamma and tumor necrosis factor alpha polymorphisms with susceptibility to vitiligo in Iranian patients

Vitiligo is a common skin disorder that is caused by selective destruction of melanocytes, resulting in disfiguring loss of pigment. There are convincing evidences that cytokines and T cell mediated immunity may have a role in its pathogenesis. Given the fact that cytokine production is under genetic control, in this study, we have investigated IFN-γ +874 T/A and TNF-α −308 G/A gene polymorphisms in a total of 176 vitiligo patients and 545 controls. IFN-γ +874 T/A and TNF-α −308 G/A gene polymorphisms were genotyped via Allele Specific Oligonucleotide PCR (ASO-PCR) method. The results showed that the TNF-α −308 G/A polymorphism was more common in vitiligo patients than controls (P = 0.0004). This difference was only significant between female patients and controls (P < 0.0001), while there was no significant difference between male patients and male controls (P = 0.90). The distribution of IFN-γ genotypes in vitiligo patients did not differ significantly from that in control subjects (P = 0.56). Since the presence of A nucleotide at position −308 of TNF-α gene is associated with increased cytokine production, therefore, the higher frequency of TNF-α −308 A allele in vitiligo patients compared to controls may be considered as a genetic susceptibility factor towards the development of vitiligo.     

Gene expression study of IL10 family genes in vitiligo skin biopsies, peripheral blood mononuclear cells and sera

Background Vitiligo is a pigmentation disorder, the cause of which is complex and not yet fully understood. There is a significant change of epidermal cytokines in involved skin of patients with vitiligo compared with uninvolved skin and skin of healthy controls, thus suggesting a possible involvement of cytokines in the pathogenesis of vitiligo. Objectives To evaluate potential roles of IL10 family cytokines (IL10, IL19, IL20, IL22 and IL24) in vitiligo. Along with the selected cytokines, we investigated subunits of the receptors (IL10RA, IL10RB, IL20RA and IL22RA1) which are involved in the signalling pathway of the cytokines. Methods Quantitative real‐time polymerase chain reaction was used to detect mRNA expression levels in samples extracted from skin biopsies and peripheral blood mononuclear cells and an enzyme‐linked immunosorbent assay was used to measure protein concentrations in serum from patients with vitiligo and healthy controls. Results IL22 is significantly associated with vitiligo, especially with the active stage of vitiligo, as shown by results of mRNA expression and supported by results of protein level in sera. IL22 may provoke inflammation which leads to destruction of melanocytes. Conclusions The actual role of IL22 during pathogenesis of vitiligo remains to be better characterized. Signal transductions of other investigated cytokines seem to be regulated on the expression level of their receptor complex subunits.     

Effects of CO2 fractional laser therapy on peripheral blood cytokines in patients with vitiligo

Vitiligo is a disease pathologically characterized by specific damage to melanocytes. The aim of this study was to explore the mechanism underlying CO2 fractional laser treatment of vitiligo by detecting the levels of Th1 cytokines (IL‐2 and IFN‐γ), Th2 cytokines (IL‐4 and IL‐10), and Th17 cytokines (IL‐17 and IL‐23) in peripheral blood. Twenty five vitiligo patients were enrolled in this study and were treated with a CO2 fractional laser four to eight times. The cytokines of 25 vitiligo patients and 20 healthy volunteers were measured by enzyme‐linked immunosorbent assay. After CO2 fractional laser therapy, six cases were cured, and the apparent efficiency was 72.0% (18/25), while the efficiency was 92.0% (23/25). Before CO2 fractional laser therapy, IL‐2 and IFN‐γ levels in vitiligo patients were higher than those in the control group, but the difference was not statistically significant (p > .05). IL‐4, IL‐10, IL‐17, and IL‐23 levels were also higher in vitiligo patients than those in the control group (p < .05). After treatment, IL‐2 and IFN‐γ levels in vitiligo patients were lower than before treatment, but the difference was not statistically significant (p > .05), while IL‐4, IL‐10, IL‐17, and IL‐23 levels were significantly lower compared with before treatment (p < .05). The results show that CO2 fractional laser treatment has a good curative effect in the treatment of vitiligo.     

Serum Th1/Th2 and macrophage lineage cytokines in leprosy; correlation with circulating CD4+ CD25highFoxP3+ T‐regs cells

Not only macrophages, T‐helper (Th)1 and Th2, but also CD4⁺ CD25^highFoxP3⁺ regulatory T cells (T‐regs) are involved in immune response to Mycobacterium leprae. We aimed to evaluate serum interleukin (IL)‐1β and IL‐12p70 (macrophage cytokines), interferon‐γ (IFN‐γ) (Th1 cytokine), IL‐4 (Th2 cytokine) and circulating CD4⁺ CD25^highFoxP3⁺ T‐regs, in untreated leprosy patients. Forty three patients and 40 controls were assessed for the mentioned cytokines using ELISA. Patients were assessed for circulating T‐regs using flow cytometry. Patients were subgrouped into tuberculoid (TT), pure neural leprosy (PNL), borderline cases, lepromatous (LL), type 1 reactional leprosy (RL1) and erythema nodosum leprosum (ENL). Serum IL‐12p70, IFN‐γ and IL‐4 were significantly higher in patients versus controls (P < 0.05). Serum IL‐4 was highest in LL and lowest in RL1 (P = 0.003). Serum IL‐1β levels was significantly higher in multibacillary versus paucibacillary patients (P = 0.006). Significantly higher T‐regs levels was detected in TT, RL1 and PNL, while the lowest levels in ENL(P < 0.001), with significant differences versus controls (P < 0.05). FoxP3 expression% was significantly lower in PNL than other patients and controls (P < 0.05). T‐regs/T‐effs was lowest in ENL(P < 0.05). IFN‐γ correlated positively with T‐regs but negatively with IL‐1β (P = 0.041&0.046 respectively), which correlated positively with T‐effs%( P = 0.05). IL‐4 correlated positively with T‐regs FoxP3 expression% (P = 0.009). We concluded that: Circulating T‐regs were increased in TT, RL1 and PNL patients, known of relatively high cell‐mediated immunity. This finding was supported by low FoxP3 expression (in PNL) and correlation between T‐regs count and IFN‐γ level. Overproduction of IL‐4 in LL may infer liability to develop ENL, with disease progression and immune hyperactivation, marked by deficient T‐regs and increased T‐regs FoxP3 expression%. IL‐1β probably has a pro‐inflammatory role in multibacillary patients as correlated with T‐effs%.     

Role of IL‐17A receptor blocking in melanocyte survival: A strategic intervention against vitiligo

Cytokines regulate immune response and inflammation and play an important role in depigmentation process of an autoimmune disease, vitiligo. We sought to determine how inflammatory cytokines influence the progression of vitiligo, and based on that, we develop a logical therapeutic intervention using primary melanocyte culture. Melanocytes were cultured and exposed to IL‐17A, IL‐1β, IFN‐γ and TGF‐β for 4 days. Melanocytes proliferation, tyrosinase assay and melanin content were measured. Real‐Time PCR was used to analyse mRNA expression of genes specific for melanocytes growth and pigmentation. Anti‐IL‐17A receptor antibody was used to block IL‐17A receptors expressed on melanocytes. Protein expression of MITF and TYR was assessed by immunofluorescence and Western blotting. A gradual decline in the melanocyte population, melanin content and tyrosinase activity was observed after different cytokine treatment. The expression of MITF and its downstream genes after blocking with anti‐IL‐17RA, an increased melanin content, increased expression of TYR, MITF along with its downstream genes, and cell proliferation was observed.     

Regulatory T‐cell cytokines in patients with nonsegmental vitiligo

In the etiopathogenesis of vitiligo, the role of suppressor cytokines, such as transforming growth factor‐β (TGF‐β) and interleukin‐10 (IL‐10), associated with regulatory T‐cells (Treg) is not completely known. In this study, the role of Treg‐cell functions in the skin of patients with nonsegmental vitiligo was investigated. Lesional and nonlesional skin samples from 30 adult volunteers ranging in age from 18 to 36 years with nonsegmental vitiligo were compared with normal skin area excision specimens of 30 benign melanocytic nevus cases as controls. All samples were evaluated staining for forkhead box P3 (Foxp3), TGF‐β, and IL‐10 using the standardized streptavidin–biotin immunoperoxidase immunohistochemistry method. Foxp3 expression was lower in lesional vitiligo skin specimens compared to controls; it was also lower in lesional vitiligo specimens than nonlesional vitiligo specimens. IL‐10 levels were lower in lesional vitiligo specimens compared to the controls, whereas IL‐10 expression was significantly lower in lesional specimens compared with nonlesional specimens. TGF‐β expression was higher in both lesional and nonlesional skin specimens of patients with vitiligo compared to controls. TGF‐β expression was lower in lesional skin specimens than nonlesional skin specimens. In addition, there was no significant correlation between Foxp3 expression with TGF‐β and IL‐10 expressions in lesional skin specimens in the vitiligo group. In this study, results supporting the contribution of Treg cells and IL‐10 deficiency to the autoimmune process were obtained. Therefore, future studies are necessary to demonstrate the definitive role of Treg‐cell functions in the etiopathogenesis of vitiligo.     

TNF‐α and IL‐10 gene polymorphisms show a weak association with pemphigus vulgaris in the Slovak population

Backround Pemphigus vulgaris is a rare chronic autoimmune disease of skin and mucous membranes, with several cytokines participating in its development. The role of their gene polymorphisms in susceptibility to the disease is, however, not fully understood. Objective The aim of our case‐control study was to investigate whether some of 22 single nucleotide polymorphisms (SNPs) in 13 cytokine genes (IL‐1α, IL‐1β, IL‐1RI, IL‐1Ra, IL‐4Rα, IL‐12, IFN‐γ, TGF‐β1, TNF‐α, IL‐2, IL‐4, IL‐6 and IL‐10) are associated with pemphigus vulgaris in the Slovak population. Methods DNA samples were obtained from 34 pemphigus vulgaris patients and 140 healthy controls of Slovak origin. Cytokine gene SNPs were determined using the polymerase chain reaction with sequence‐specific primers (PCR‐SSP) method. Results We found a weak association between pemphigus vulgaris and polymorphic variants in TNF‐α and IL‐10 genes only, with haplotypes TNF‐α–308G/–238G and IL‐10 –1082A/–819C/–592C being significantly overrepresented in pemphigus vulgaris patients (TNF‐α GG: 94.12% vs. 82.86%, P = 0.0216; IL‐10 ACC: 44.12% vs. 30.00%, P = 0.0309). Conclusions Our preliminary results suggest that certain TNF‐α and IL‐10 gene polymorphisms might contribute to genetic susceptibility to pemphigus vulgaris; however, their overall impact on disease development will be rather limited.     

Association between oral lichenoid reactions and amalgam restorations

Background The aim of this study was to perform a clinical assessment of the association between oral lichenoid reactions (OLR) and amalgam restorations and to determine the salivary concentrations of interleukin‐6 (IL‐6) and IL‐8 before and after replacement of the amalgam restorations. Methods The study included 20 patients with OLR and 20 healthy volunteers, who were examined between 2001 and 2005 at the Oral Medicine Unit of the Medical Faculty University of Rijeka. All patients were skin patch tested by an experienced physician. Saliva samples were collected, prepared and analysed for IL‐6 and IL‐8 concentrations using enzyme‐linked immunosorbent assay. Results Sixteen out of 20 patch‐tested patients showed a sensitization to inorganic mercury or amalgam. Total replacement of all amalgam fillings was carried out on 20 patients with fillings based on composite resin, gold, porcelain or a combination of these. Sixteen out of 20 patients showed complete healing of OLR; three patients had marked improvement, whereas one patient showed no improvement. Levels of IL‐6 detected before replacement were significantly higher than IL‐6 levels following the replacement (P = 0.003). The IL‐8 levels measured before replacement procedure were significantly higher than the IL‐8 levels after replacement of the fillings (P < 0.001). Conclusions On the basis of clinical observations, restorative therapy resulted in tissue healing. Following the replacement of amalgam fillings with fillings based on other restorative materials, levels of both IL‐6 and IL‐8 shifted towards normal, as measured in healthy subjects.     

Distinct age‐matched serum biomarker profiles in patients with cutaneous T‐cell lymphoma

Immunological functions decline with age. Because MS/SzS predominately affects the elderly, it is important to distinguish age‐related from cancer‐specific changes. Also, MF and SzS are malignancies of CD4⁺ T‐lymphocytes, further compromising an immune state of the patients. The objectives of this study were to distinguish disease‐specific immunological deterioration by performing comparative age ‐ matched Luminex multiplex assessment of 34 serum biomarkers between patients with MF/SzS, HIV‐infected individuals and normal controls. Controlling for age, expression level appears to significantly differ between patients with MF/SzS and controls for the following biomarkers: G‐CSF, IL‐5, MIP‐1β, TNF‐α, VEGF, EOTAXIN, IL‐8, IL‐12, IL‐2R, IP10, MCP‐1, MIG, TNFR1 and TNFR2 (P < 0.05), while others showed normal age‐related changes. Interestingly, cluster analysis placed MF/SzS profiles closer to HIV. This further underscores an immunologically compromised state of patients with MF/SzS and suggests its potential self‐perpetuating role in disease progression.     

Expression analysis of PD‐1 and Tim‐3 immune checkpoint receptors in patients with vitiligo; positive association with disease activity

The contribution of immune checkpoint receptors in the immunopathogenesis of various autoimmune diseases has been addressed in previous reports. In this study,  the expression profile of T‐cell immunoglobulin and mucin‐domain containing‐3 (Tim‐3) and programmed cell death‐1 (PD‐1) checkpoint molecules was investigated in CD8⁺ T cells of Vitiligo patients. The association of Tim‐3 and PD‐1 expression with disease activity was also explored. The frequency of Tim‐3⁺/PD‐1⁺/CD8⁺ T cells in 30 patients with vitiligo and 30 sex‐ and age‐matched controls was determined by flow cytometry. CD8⁺ T cells were then positively isolated by magnetic beads, and the mRNA expression of PD‐1 and Tim‐3 was determined by TaqMan‐based real‐time PCR. To measure the cytokines production, PBMCs were stimulated with PMA/ionomycin and concentrations of IL‐4, IFN‐γ and TNF‐α were measured in culture supernatants by ELISA. Disease activity of patients with vitiligo was determined using the Vitiligo Area Severity Index. Patients with vitiligo have significantly shown more expression of Tim‐3 and PD‐1 on their CD8⁺ T cells compared with controls. Expression analysis of Tim‐3 mRNA, but not PD‐1, confirmed the results obtained from flow cytometry. While the production levels of TNF‐α and IFN‐γ were found higher by patients with vitiligo, IL‐4 production was lower in patients compared with controls. A direct association was observed between the Tim‐3 and PD‐1 expression and also the production of pro‐inflammatory cytokines with disease activity of patients with vitiligo. Our results indicate that Tim‐3 and PD‐1 are involved in immune dysregulation mechanisms of CD8⁺ T cells in vitiligo and may introduce as potential biomarkers for disease progression and targeted immunotherapy.     

Fas-FasL interaction in cytotoxic T cell-mediated vitiligo: The role of lesional expression of tumor necrosis factor-α and interferon-γ in Fas-mediated melanocyte apoptosis

Vitiligo is an acquired skin depigmentation disorder resulting from the selective loss of epidermal melanocytes, and previous studies have suggested that a T lymphocyte-mediated mechanism has a role in melanocyte loss. Although Fas-Fas ligand (FasL) interactions are important for T lymphocytes to mediate cytotoxicity, there are only few reports examining the involvement of the Fas-FasL pathway in vitiligo using in vivo mouse models. In addition, there have been no reports concerning Fas-mediated apoptosis in human melanocytes in vitro. In this study, we found that the Fas-mediated pathway is involved in cytotoxic T lymphocyte (CTL)-dependent vitiligo in a mouse model and FasL-induced apoptosis of human melanocytes. Tumor necrosis factor (TNF)-α and interferon (IFN)-γ, the expression levels of which have been reported to be elevated in lesional skin of patients with vitiligo, synergistically upregulated Fas expression on human melanocytes but inhibited the Fas-mediated apoptosis. Treatment with TNF-α and IFN-γ synergistically upregulated the expression of the anti-apoptotic genes, c-IAP2, c-FLIP and MCL1. A siRNA knock-down study showed that c-FLIP and MCL1, but not c-IAP2, were involved in inducing synergistic inhibitory effects on Fas-mediated apoptosis. Furthermore, we found that FasL and TNF-related apoptosis - inducing ligand (TRAIL) synergistically induced apoptosis on human melanocytes. In conclusion, our results suggest that the Fas-FasL pathway is involved in CTL-dependent vitiligo and the elevated expression levels of TNF-α and IFN-γ in lesional skin may act synergistically on melanocytes to suppress Fas-mediated apoptosis.     

Cytokine gene polymorphisms in bullous pemphigoid in a Chinese population

Background Bullous pemphigoid (BP) is an autoimmune bullous disease mostly associated with autoantibodies to the hemidesmosomal BP autoantigens BP180 and BP230. High levels of interleukin (IL)‐1β, IL‐4, IL‐5, IL‐6, IL‐8, IL‐10, IL‐13, tumour necrosis factor (TNF)‐α and interferon (IFN)‐γ have been detected in skin lesions or sera of patients with BP. Cytokine gene polymorphisms may affect cytokine production and contribute to susceptibility to autoimmune diseases. Until now, no cytokine gene polymorphism study has been conducted on patients with BP. Objectives We aimed to determine whether the genetic polymorphisms of the cytokine genes might influence the development of BP. Methods DNA samples were obtained from 96 BP patients and 174 control subjects. Using direct sequencing and microsatellite genotyping, we examined 23 polymorphisms in 11 cytokine genes including the IL‐1α, IL‐1β, IL‐1 receptor antagonist, IL‐4, IL‐6, IL‐8, IL‐10, IL‐13, IL‐4 receptor, TNF‐α and IFN‐γ genes. Results Although the BP patients were more likely to carry the ?511T and ?31C alleles of the IL‐1β gene (P = 0·04), the significance disappeared after correction for multiple testing (P_c). There was complete linkage disequilibrium between the ?511T and ?31C alleles of the IL‐1β gene. In female patients with BP, the associations with IL‐1β (?511T) and (?31C) alleles were much stronger (68% vs. 40·6%, odds ratio = 3·11, P_c = 0·006). No significantly different allelic and genotypic distributions of other cytokine gene polymorphisms could be found between the patients with BP and controls. Moreover, no association with the extent of disease involvement (localized or generalized) was observed. Conclusions The IL‐1β (?511) and (?31) polymorphisms were significantly associated with BP in women. The other genetic polymorphisms of cytokine genes that we analysed do not appear to be associated with BP susceptibility in our Chinese population.     

Reduction of inflammatory slan (6‐sulfo LacNAc) dendritic cells in psoriatic skin of patients treated with etanercept

Dermal dendritic cells (DCs) play a central role in the immunopathology of psoriasis. We previously identified slanDCs as pro‐inflammatory TNF‐α, IL‐23‐ and IL‐12‐producing DCs in human blood and as prominent inflammatory dermal TNF‐α secreting and CD11c‐positive DC subset in psoriasis. Here, we ask for the effects of TNF‐α‐inhibition on inflammatory slanDCs in skin and blood of 10 patients with psoriasis during 24 weeks of treatment with etanercept. Treatment with etanercept reduced the frequency of dermal slanDCs but did not induce apoptosis as determined by lack of increased active caspase‐3‐expression. In parallel, we found increased frequencies of slanDCs in blood which expressed lower levels of HLA‐DR. Stimulating slanDCs isolated from the blood of healthy donors in vitro induced a strong production of IL‐1β, IL‐6, IL‐23 and IL‐12p70. This capacity was efficiently reduced in the presence of etanercept, thereby indicating that TNF‐α is an autocrine stimulus for maturation and pro‐inflammatory cytokine production of slanDCs. In vivo, we noticed that treatment with etanercept did reduce the number of dermal slanDCs in parallel to the overall expression of TNF‐α and IL‐23p19. However, successful treatment did not down‐regulated the percentage of dermal slanDCs that stained positive for TNF‐α and IL‐23p19 indicating that remaining slanDCs kept their pro‐inflammatory capacity. This study provides novel insights into the immune regulatory properties of etanercept at the level of inflammatory slanDCs in vivo in skin and blood as well as in vitro.     

Heparinoid suppresses Der p‐induced IL‐1β production by inhibiting ERK and p38 MAPK pathways in keratinocytes

Epidermal keratinocytes initiate skin inflammation by activating immune cells. The skin barrier is disrupted in atopic dermatitis (AD) and epidermal keratinocytes can be exposed to environmental stimuli, such as house dust mite (HDM) allergens. We showed previously that HDM allergens activate the NLRP3 inflammasome of keratinocytes, thereby releasing pro‐inflammatory cytokines. Heparinoid is an effective moisturizer for atopic dry skin. However, a recent report showed that heparinoid treatment can improve inflammation of lichen planus. Therefore, we hypothesized that it acts on epidermal keratinocytes not only as a moisturizer, but also as a suppressant of the triggers of skin inflammation. We found that HDM allergen‐induced interleukin (IL)‐1β release from keratinocytes was inhibited significantly by heparinoid pretreatment without affecting cell viability. However, heparinoid did not affect caspase‐1 release, suggesting that heparinoid did not affect HDM allergen‐induced inflammasome activation. Heparinoid treatment not only decreased intracellular levels of pro‐IL‐1β, but also suppressed IL‐1β messenger RNA (mRNA) expression in keratinocytes. Among the intracellular signalling pathways, the activation of extracellular signal‐regulated kinase and p38 pathways, which are required for IL‐1β expression in keratinocytes, was inhibited by heparinoid treatment. The inhibitory effect of heparinoid on IL‐1β mRNA expression was also confirmed with living skin equivalents. Our results demonstrated that heparinoid suppresses the initiation of keratinocyte‐mediated skin inflammation.     

Melanocyte‐protective effect of afzelin is mediated by the Nrf2‐ARE signalling pathway via GSK‐3β inactivation

Vitiligo is an acquired condition characterized by depigmented, cutaneous lesions that result from the death of pigment‐producing cells, melanocytes. The occurrence of oxidative stress has been proposed as a pathogenetic mechanism for melanocyte degeneration in vitiligo. Therefore, in this study, we investigated the cytoprotective effects of afzelin against oxidative stress and its mechanism of action in human epidermal melanocytes. We found that afzelin significantly inhibited hydrogen peroxide‐induced cell death, cellular reactive oxygen species production and lipid peroxidation in melanocytes. In an antioxidant response element (ARE)‐luciferase reporter assay, afzelin increased ARE‐luciferase reporter activity in a concentration‐dependent manner. Consistently, the expression of antioxidant genes, including NF‐E2‐related factor 2 (Nrf2), haem oxygenase‐1 (HO‐1) and catalase, was enhanced by afzelin treatment. Nuclear translocation of Nrf2 also increased in response to afzelin treatment. In addition, the phosphorylation of glycogen synthase kinase‐3β (GSK‐3β) was induced by afzelin treatment. The enhancement of HO‐1 gene expression by afzelin treatment was reduced by Nrf2‐siRNA expression. Furthermore, we found that the expression of Nrf2‐siRNA significantly attenuated the cytoprotective effect of afzelin against hydrogen peroxide. These data suggest that the cytoprotective effects of afzelin against hydrogen peroxide may be mediated by Nrf2‐ARE signalling via GSK‐3β inactivation. Our data suggest the novel use of afzelin for the prevention of oxidative stress‐induced damage in melanocytes and its potential as a therapeutic agent for vitiligo.     

Abnormal nuclear expression of aquaporin-3 in lesional and perilesional skin of vitiligo patients: A novel immunohistochemical finding

Background

Vitiligo is a skin disease characterized by a complex etiopathogenesis. Keratinocyte apoptosis may play a role in vitiligo pathogenesis. Aquaporin-3 (AQP-3) is an aqua-glyceroporin that controls keratinocyte proliferation and differentiation.

Aim

To assess the immunohistochemical expression of AQP-3 in lesional and perilesional skin of vitiligo patients compared to healthy control skin.

Methods

A total of 20 patients with generalized non-segmental vitiligo and 20 age- and sex-matched healthy controls were included. Lesional and perilesional skin of vitiligo patients, as well as normal skin of control subjects, were biopsied. The immunohistochemical expression of AQP3 in the epidermis was examined.

Results

Compared to control skin, both lesional and perilesional skin showed a significant reduction in the intensity of membranous staining of AQP-3 (p < 0.001, p = 0.002, respectively). Moreover, the membrano-cytoplasmic pattern of AQP-3 staining was significantly detected in 80% of lesions and 85% of perilesional biopsies, while it was absent in control skin (p < 0.001). Additionally, nuclear AQP-3 expression was significantly detected in 35% of lesions and 55% of perilesional biopsies, while it was not detected in control skin (p = 0.012, p < 0.001, respectively). No statistically significant difference was detected between lesional and perilesional skin.

Conclusions

To our knowledge, this is the first immunohistochemical research to show a significant abnormal nuclear expression of AQP-3 in lesional and perilesional skin of vitiligo patients. This abnormality may reflect impaired functions of AQP-3, leading to keratinocyte apoptosis with subsequent melanocyte death and development of vitiligo.     

Effects of Coccoloba uvifera L. on UV‐stimulated melanocytes

Background: Exposure to ultraviolet (UV) radiation induces generation of reactive oxygen species, production of proinflammatory cytokines and melanocyte‐stimulating hormone (MSH) as well as increase in tyrosinase activity. The potential photoprotective effects of Coccoloba uvifera extract (CUE) were evaluated in UV‐stimulated melanocytes. Methods: Human epidermal melanocytes were used as an in vitro model to evaluate the effects of CUE on the production interleukin‐1α (IL‐1α), tumor necrosis factor α (TNF‐α), and α‐MSH under basal and UV‐stimulated conditions. Antioxidant and anti‐tyrosinase activities were also evaluated in membrane lipid peroxidation and mushroom tyrosinase assay, respectively. Results: Coccoloba uvifera L. showed antioxidant and anti‐tyrosinase activities and also inhibited the production of IL‐1α, TNF‐α and α‐MSH in melanocytes subjected to UV radiation (P<0.01). Moreover, CUE inhibited the activity of tyrosine kinase in cell culture under basal and UV radiation conditions (P<0.001), corroborating the findings of the mushroom tyrosinase assay. Conclusion: This study supports the photoprotective potential of CUE.