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

Identification of TNF-α as Major Susceptible Risk Locus for Vitiligo: A Systematic Review and Meta-Analysis Study in the Asian Population

INTRODUCTION

Vitiligo is a common depigmentation disorder characterized by defined white patches on the skin and affecting around 0.5% to 2% of the general population. Genetic association studies have identified several pre-disposing genes and single nucleotide polymorphisms (SNPs) for vitiligo pathogenesis; nonetheless, the reports are often conflicting and rarely conclusive. This comprehensive meta-analysis study was designed to evaluate the effect of the risk variants on vitiligo aetiology and covariate stratified vitiligo risk in the Asian population, considering all the studies published so far.

METHODS

We followed a systematic and comprehensive search to identify the relevant vitiligo-related candidate gene association studies in PubMed using specific keywords. After data extraction, we calculated, for the variants involved, the study-level unadjusted odds ratio, standard errors, and 95% confidence intervals by using logistic regression with additive, dominant effect, and recessive models using R software package (R, 3.4.2) "metafor." Subgroup analysis was performed using logistic regression (generalized linear model; "glm") of disease status on subgroup-specific genotype counts. For a better understanding of the likely biological function of vitiligo-associated variant obtained through the meta-analysis, in silico functional analyses, through standard publicly available web tools, were also conducted.

RESULTS

Thirty-one vitiligo-associated case-control studies on eleven SNPs were analysed in our study. In the fixed-effect meta-analysis, one variant upstream of TNF-α gene: rs1800629 was found to be associated with vitiligo risk in the additive (p = 4.26E-06), dominant (p = 1.65E-7), and recessive (p = 0.000453) models. After Benjamini-Hochberg false discovery rate (FDR) correction, rs1800629/TNF-α was found to be significant at 5% FDR in the dominant (padj = 1.82E-6) and recessive models (padj = 0.0049). In silico characterization revealed the prioritized variant to be regulatory in nature and thus having potential to contribute towards vitiligo pathogenesis.

CONCLUSION

Our study constitutes the first comprehensive meta-analysis of candidate gene-based association studies reported in the whole of the Asian population, followed by an in silico analysis of the vitiligo-associated variant. According to the findings of our study, TNF-α single nucleotide variant rs1800629G>A has a risk association, potentially contributing to vitiligo pathogenesis in the Asian population.

The role of cytokines and vitamin D in vitiligo pathogenesis

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

Current Debates on Etiopathogenesis and Treatment Strategies for Vitiligo

Vitiligo is an acquired, chronic, and progressive depigmentation or hypopigmentation characterized by the destruction of melanocytes and the occurrence of white patches or macules in the skin, mucosal surface of eyes, and ears. Melanocytes are the melanin pigment-producing cells of the skin which are destroyed in pathological conditions called vitiligo. Approximately 0.5 - 2.0% of the population is suffering from vitiligo, and a higher prevalence rate of up to 8.8% has been reported in India. It is caused by various pathogenic factors like genetic predisposition, hyperimmune activation, increased oxidative stress, and alteration in neuropeptides level. Genetic research has revealed a multi- genetic inheritance that exhibits an overlap with other autoimmune disorders. However, melanocytes specific genes are also affected (such as DDR1, XBP1, NLRP1, PTPN22, COMT, FOXP3, ACE, APE, GSTP1, TLR, SOD, and CTLA-4). A number of therapeutic options are employed for the treatment of vitiligo. The topical corticosteroids and immunomodulators are currently in practice for the management of vitiligo. Phototherapies alone and in combinations with other approaches are used in those patients who do not respond to the topical treatment. The main focus of this review is on the etiopathological factors, pharmacological management (phototherapy, topical, systemic, and surgical therapy), and herbal drugs used to treat vitiligo.

Meta-analysis for association of TNFA-308(G > A) SNP with vitiligo susceptibility

Vitiligo is an autoimmune progressive skin depigmenting disease. Tumor necrosis factor alpha (TNF-α) is a pro-inflammatory cytokine and plays a crucial role in vitiligo development. Since there are conflicting results and consensus is lacking for the association of the TNFA gene -308 G > A polymorphism with vitiligo susceptibility; we performed a meta-analysis of all the available studies to investigate the association of TNFA -308 G > A polymorphism with vitiligo risk. 11 studies involving 2199 vitiligo patients and 3083 controls were included in the meta-analysis. The meta-analysis revealed an increased vitiligo risk with "AA", "GA" and "AA" + "GA" genotypes and 'A' allele in the overall (p = 0.006, p = 0.003, p = 0.001 & p = 0.003) and Egyptian populations (p = 0.001, p < 0.00001, p < 0.00001 & p = 0.002). Moreover, we found association for "GA" and "AA" + "GA" genotypes in Asian population (p = 0.0009 & p = 0.005) and for 'A' allele in Asian and middle eastern populations (p = 0.04 & p = 0.0002). Interestingly the disease activity based analysis revealed significant association for "GA", "AA" + "GA" genotypes and 'A' allele with active vitiligo patients in the North American population (p = 0.02). Moreover, we found significant association for "GA", "AA" + "GA" genotypes and 'A' allele with localized vitiligo in overall (p = 0.02, p = 0.02 & p = 0.04) and Asian (p = 0.004, p = 0.003 & p = 0.01) populations. Overall, our meta-analysis suggests the involvement of susceptible 'A' allele with: i) vitiligo susceptibility in overall population and specifically with Asian, Middle Eastern and Egyptian populations; ii) vitiligo disease activity in North American population and iii) localized vitiligo in overall population and specifically in Asian population.

Role of Amine Neurotransmitters and Their Receptors in Skin Pigmentation: Therapeutic Implication

Skin pigmentation can occur due to increased melanin, including melanocyte proliferation, melanin biosynthesis, or melanocyte migration. There are many factors that influence the melanin production process, but the role of neurotransmitters in this process is still unclear. We found that histamine and serotonin influence the different stages of melanogenesis and melanogenesis, which increase melanogenesis. Since then, several related papers have been published, and from these papers, it has been recognised that the role of neurotransmitters in skin-pigment-related diseases needs to be summarised. By introducing the role of neurotransmitters in the regulation of various pigment disorders, including vitiligo and melasma, through this review, many researchers can be expected to try to apply neurotransmitter-related agonists and antagonists as treatments for skin pigment disorders.

Tumor Necrosis Factor-alpha affects melanocyte survival and melanin synthesis via multiple pathways in vitiligo

Tumor necrosis factor-α (TNF-α) is a major mediator of inflammation and its increased levels have been analyzed in vitiligo patients. Vitiligo is a depigmentary skin disarray caused due to disapperance of functional melanocytes. The aim of the study was to investigate the role of TNF-α in melanocyte biology, analyzing candidate molecules of melanocytes and immune homeostasis. Our results showed increased TNF-α transcripts in vitiligenous lesional and non-lesional skin. Melanocytes upon exogenous stimulation with TNF-α exhibited a significant reduction in cell viability with elevated cellular and mitochondrial ROS and compromised complex I activity. Moreover, we observed a reduction in melanin content via shedding of dendrites, down-regulation of MITF-M, TYR and up-regulation of TNFR1, IL6, ICAM1 expression, whereas TNFR2 levels remain unaltered. TNF-α exposure stimulated cell apoptosis at 48 h and autophagy at 12 h, elevating ATG12 and BECN1 transcripts. Our novel findings establish the functional link between autophagy and melanocyte destruction. Overall, our study suggests a key function of TNF-α in melanocyte homeostasis and autoimmune vitiligo pathogenesis.

Tumor necrosis factor (TNF)-α- 308 G/A gene polymorphism (rs1800629) in Egyptian patients with alopecia areata and vitiligo, a laboratory and in silico analysis

Purpose & methods

Several single-nucleotide polymorphisms (SNPs) in the promoter region of the TNF-α gene can cause variations in the gene regulatory sites and act as risk factors for some autoimmune disorders as alopecia areata (AA) and vitiligo. This study aimed to detect the serum TNF-α (sTNF) level (by ELISA) and the rs1800629 (by real-time PCR) among AA and vitiligo Egyptian patients and to determine their relation with disease duration and severity. In silico analysis of this SNP to study the molecular regulation of the mutant genotypes was also done.

Results

In AA patients, no risk was associated with the mutant genotypes vs. the normal genotype, or with A allele vs. G allele. The risk of vitiligo was significantly higher with the G/A and A/A genotypes compared with HCs (p = 0.011). Similarly, a significantly increased risk was noted in patients with A allele vs. G allele (p<0.0001). In AA and vitiligo patients, a significant increase in sTNF-α levels was noted in the mutant G/A genotypes vs. the normal G/G genotype (p<0.0001) and in the A allele vs the G allele (p<0.0001). According to the in silico analysis, this SNP could mainly affect the SP1 transcription factor binding site with subsequent effect on TNF-α expression.

Conclusion

According to results of the laboratory and the in silico study, the mutant TNF-α (308) genotypes were risk factors that conferred susceptibility to vitiligo among Egyptian patients but had no effect on the susceptibility to AA.

Association Analysis of Tumor Necrosis Factor Alpha Promoter Polymorphisms and Vitiligo Susceptibility in South Indian Tamils

Tumor necrosis factor alpha (TNF-α) has been associated with the pathogenesis of several autoimmune diseases. Also, various studies in different ethnics showed an association between TNF-α gene polymorphisms and susceptibility to vitiligo. The paucity of genetic data led us to undertake this study to evaluate the association of five TNF-α SNPs (rs1799964, rs1800630, rs1799724, rs1800629, and rs361525) with the development of vitiligo in South Indian Tamils. A total of 264 vitiligo patients and 264 healthy controls were recruited and TNF-α genotyping was performed using amplification-refractory mutation system polymerase chain reaction and TaqMan allele discrimination assay. Circulatory TNF-α levels were measured by enzyme-linked immunosorbent assay. We observed that a single polymorphic allele A in the promoter region -308 (rs1800629) conferred significant risk to develop vitiligo (p = 0.0002, OR = 1.70, 95% CI = 1.28-2.25), whereas the other polymorphisms failed to contribute to disease risk (p > 0.05). From the constructed haplotypes, TCCAG was found to be a significant risk factor for vitiligo (p < 0.05). Also, a strong linkage disequilibrium was observed between the following SNPs: (1) rs1799964 and rs1800629 (2) rs1800630 and rs1799724 (D' = 0.90). Analysis of the influence of genotype on phenotypes revealed that the A allele of rs361525 was a risk factor for vitiligo in females (p = 0.04, OR = 0.45, 95% CI = 0.21-0.95), whilst the rs1800629 allele conferred protection against early disease onset (p < 0.05). A statistically significant difference in plasma TNF-α levels was found between cases and controls (p < 0.05). The TNF-α -308A allele and TCCAG haplotype were identified as genetic risk factors for vitiligo susceptibility in South Indian Tamils.

Involvement of Interferon-γ + 874A/T Polymorphism in the Pathogenesis of and Therapeutic Response to Immune Thrombocytopenia

BACKGROUND

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by symptoms of thrombocytopenia and bleeding due to production of autoantibodies against platelets. Recently, the occurrence of polymorphisms has been identified as one of the main causes of disease onset.

METHODS

To conduct this study, we recruited 140 patients and control individuals with no history of platelet loss. After collection of specimens, the prevalence of interferon-γ polymorphism was evaluated using the allele-specific oligonucleotide-polymerase chain reaction (ASO-PCR) technique and confirmed by sequencing techniques.

RESULTS

The results showed that the frequency of the AA genotype was higher in the control group, compared with patients with ITP; however, in the acute and chronic groups, the frequency of the AT genotype was higher than that of the AA genotype. We also discovered that there was no significant correlation between platelet counts before and after treatment, nor in its related parameters with interferon (IFN)-γ polymorphism.

CONCLUSION

rs2430561 does not seem to have any role in ITP pathogenesis and treatment response.

Association Between the Interferon Gamma 874 T/A Polymorphism and the Severity of Valvular Damage in Patients with Rheumatic Heart Disease

Interferon gamma (IFN-γ) is a multifunctional cytokine that plays an important role in modulating almost all phases of the immune response and may be responsible for the increased valvular fibrosis and calcification in the pathogenesis of rheumatic heart disease (RHD). The aim of this study was to investigate the possible relationship between the IFN-γ +874 T/A polymorphism and the severity of valvular damage in the Turkish population. The IFN-γ genotypes were determined in 152 RHD patients and 151 healthy controls by ARMS-PCR. Differences in genotype distribution between patients with RHD and control were evaluated by the χ² test. All statistical analyses were performed with SPSS 15.0 Software program. Frequency of the AA genotype was found to be significantly lower and the TT genotype significantly higher in the RHD group compared to controls (p = 0.002 and p = 0.018, respectively). The TT genotype was found to be significantly higher (26.8% vs. 9.1%, p = 0.009) and the AA genotype significantly lower (29.1% vs. 8.2%, p = 0.001) in the severe valvular disease (SVD) group compared to mild valvular disease group. In the SVD group, 79 patients had mitral balloon valvotomy and/or mitral valve replacement and had significantly higher TT genotype compared to patients with medical follow-up (30.4% vs. 19%, p = 0.001). The data demonstrated that TT genotype is associated with both RHD and the severity of RHD.

Genetic variants of interferon-gamma and its mRNA expression and inflammatory parameters in the pathogenesis of vitiligo

Although genetics plays an essential role in the pathogenesis of vitiligo, vitiligo pathogenesis is still unclear. Our aim was to investigate the role of IFN-γ expression and polymorphism in vitiligo susceptibility and whether intercellular adhesion molecule-1 (ICAM-1), tumor necrosis factor (TNF)-α, and TNF-β play a role in vitiligo pathogenesis as important inflammatory parameters. Eighty-five patients with vitiligo and 90 controls were investigated for IFN-γ gene expression by quantitative real-time PCR and genotyped for IFN-γ +874T/A (rs2430561) and IFN-γ +2109A/G (rs1861494) gene polymorphisms by sequence-specific primer (SSP)-PCR and PCR-restriction fragment length polymorphism (RFLP), respectively. Serum levels of inflammatory parameters were measured using ELISA. Frequencies of the +874 TT genotype and T allele were significantly higher in patients with active vitiligo than in stable patients (P = 0.01 and 0.03, respectively). Calculation of odds ratio suggested a 1.7-fold increased risk of vitiligo in individuals having the TA haplotype. We observed overexpression of IFN-γ mRNA with elevated serum levels of IFN-γ, ICAM-1, TNF-α, and TNF-β in patients with vitiligo when compared with the control group (P = 0.001, for all). In addition, these levels were elevated in patients with active vitiligo compared with stable patients with vitiligo (P = 0.008, 0.006, 0.01, 0.01, and 0.03, respectively), which suggests the involvement of these cytokines in disease activity. In conclusion, IFN-γ is a promising immunological marker in vitiligo pathogenesis.

Vitiligo blood transcriptomics provides new insights into disease mechanisms and identifies potential novel therapeutic targets

BACKGROUND

Significant gaps remain regarding the pathomechanisms underlying the autoimmune response in vitiligo (VL), where the loss of self-tolerance leads to the targeted killing of melanocytes. Specifically, there is incomplete information regarding alterations in the systemic environment that are relevant to the disease state.

METHODS

We undertook a genome-wide profiling approach to examine gene expression in the peripheral blood of VL patients and healthy controls in the context of our previously published VL-skin gene expression profile. We used several in silico bioinformatics-based analyses to provide new insights into disease mechanisms and suggest novel targets for future therapy.

RESULTS

Unsupervised clustering methods of the VL-blood dataset demonstrate a "disease-state"-specific set of co-expressed genes. Ontology enrichment analysis of 99 differentially expressed genes (DEGs) uncovers a down-regulated immune/inflammatory response, B-Cell antigen receptor (BCR) pathways, apoptosis and catabolic processes in VL-blood. There is evidence for both type I and II interferon (IFN) playing a role in VL pathogenesis. We used interactome analysis to identify several key blood associated transcriptional factors (TFs) from within (STAT1, STAT6 and NF-kB), as well as "hidden" (CREB1, MYC, IRF4, IRF1, and TP53) from the dataset that potentially affect disease pathogenesis. The TFs overlap with our reported lesional-skin transcriptional circuitry, underscoring their potential importance to the disease. We also identify a shared VL-blood and -skin transcriptional "hot spot" that maps to chromosome 6, and includes three VL-blood dysregulated genes (PSMB8, PSMB9 and TAP1) described as potential VL-associated genetic susceptibility loci. Finally, we provide bioinformatics-based support for prioritizing dysregulated genes in VL-blood or skin as potential therapeutic targets.

CONCLUSIONS

We examined the VL-blood transcriptome in context with our (previously published) VL-skin transcriptional profile to address a major gap in knowledge regarding the systemic changes underlying skin-specific manifestation of vitiligo. Several transcriptional "hot spots" observed in both environments offer prioritized targets for identifying disease risk genes. Finally, within the transcriptional framework of VL, we identify five novel molecules (STAT1, PRKCD, PTPN6, MYC and FGFR2) that lend themselves to being targeted by drugs for future potential VL-therapy.

Association of genetic polymorphisms in interferon-γ, interleukin-6 and transforming growth factor-β1 gene with oral lichen planus susceptibility

BACKGROUND

Oral lichen planus (OLP) is a premalignant mucocutaneous disease in which genetic factors and immune responses play a major role. Cytokines play an important role in the pathogenesis and disease progression of OLP. The aim of this study was to investigate the impact of gene polymorphisms of T helper cell subtype Th1 and Th2 cytokines, interferon-gamma (IFN-γ), interleukin-6 (IL-6) and transforming growth factor (TGF)-β1 on OLP susceptibility in a Saudi cohort.

METHODS

Forty two unrelated patients with OLP and 195 healthy controls were genotyped for IFN-γ (874A/T), IL-6 (174G/C) and TGF-β1 (509C/T) polymorphisms.

RESULTS

The frequency of genotype AT of IFN-γ (874A/T) was significantly higher while genotype AA was lower in OLP patients as compared to controls (P < 0.05). The frequency of T containing genotypes (AT + TT) was also higher in OLP patients as compared to that in controls (P = 0.003). The frequencies of allele T was higher while that of allele A lower in patients than the controls however the difference was not statistically significant (P = 0.07). There was no significant difference in the frequencies of alleles and genotypes of IL-6 (174G/C) and TGF-β1 (509C/T) polymorphisms between patient and control groups. These results indicated that genotype AT of IFN-γ (874A/T) polymorphism is associated with OLP risk and genotype AA is protective to OLP. On the other hand the polymorphisms IL-6 (174G/C) and TGF-β1 (509C/T) may not be associated with OLP risk in our population.

CONCLUSION

It is concluded that IFN-γ (874A/T) polymorphism is associated with the susceptibility of OLP, however further studies with large sample size involving different ethnic populations should be conducted to strengthen our results.

Association between interferon-γ +874 T/A polymorphism and susceptibility to autoimmune diseases: a meta-analysis

OBJECTIVE

The aim of this study was to explore whether the interferon (IFN)-γ +874 T/A polymorphism plays a role in modifying the risk of autoimmune diseases.

METHODS

A meta-analysis was conducted on the association between the IFN-γ +874 T/A polymorphism and autoimmune diseases.

RESULTS

Eighteen studies with a total of 2952 patients and 3832 controls were included in the meta-analysis. The meta-analysis revealed no association between autoimmune diseases and the IFN-γ +874 T allele in all study subjects (odds ratio (OR)=1.023, 95% confidence interval (CI) = 0.894-1.171, p = 0.738), but stratification by ethnicity indicated an association between the IFN-γ +874 T allele and autoimmune diseases in Latin American subjects (OR = 0.780, 95% CI = 0.629-0.953, p = 0.015). Meta-analysis also revealed an association between autoimmune diseases and the IFN-γ +874 T/A polymorphism in Caucasian and Middle Eastern subjects under a dominant inheritance model (OR = 0.686, 95% CI = 0.489-0.964, p = 0.003; OR = 1.414, 95% CI = 1.102-1.813, p = 0.006). Meta-analysis by autoimmune disease type indicated an association between ITP and the IFN-γ +874 T allele (OR = 1.753, 95% CI = 1.228-2.503, p = 0.002), but not for vasculitis, vitiligo, and auto-immune thyroid disease. Meta-analysis also showed a significant association between the IFN-γ +874 T/A polymorphism and systemic lupus erythematosus (SLE) under the dominant model (OR = 1.668, 95% CI = 1.114-2.497, p = 0.013).

CONCLUSIONS

This meta-analysis indicates that the IFN-γ +874 T/A polymorphism may play a significant role in modifying the risk of autoimmune diseases in Caucasian, Latin American, and Middle Eastern subjects, and in particular shows that the IFN-γ +874 T/A polymorphism is associated with increased genetic susceptibility to idiopathic thrombocytopenic purpura and SLE.

The association between tumor necrosis factor-α-308 G/A polymorphism and risk for vitiligo: a meta-analysis

BACKGROUND

The contribution of tumor necrosis factor-α (TNF-α)-308 G/A gene polymorphism (rs1800629) to risk for vitiligo is subject to controversy.

OBJECTIVES

The fundamental purpose of the present meta-analysis was to investigate large-scale evidence to determine the overall association between TNF-α-308 G/A polymorphism and susceptibility to vitiligo.

METHODS

A literature search of the PubMed, EMBASE, Web of Science, and China National Knowledge Infrastructure (CNKI) databases was conducted to identify all studies referring to an association between TNF-α-308 G/A polymorphism and vitiligo published to June 1, 2014. The principal outcome measure for evaluating the strength of the association was the crude odds ratio (OR) along with the corresponding 95% confidence interval (CI). Data were extracted, and statistical analyses were implemented using stata Version 12.0.

RESULTS

Data for a total of 1505 vitiligo cases and 2253 controls from five case-control studies concentrating on the association between TNF-α-308 G/A polymorphism and vitiligo were included in this meta-analysis. Combined analysis revealed there to be no association between this polymorphism and susceptibility to vitiligo in five genetic models under random-effects models. A subgroup analysis by clinical type also demonstrated the absence of any association between TNF-α-308 G/A polymorphism and generalized vitiligo. However, a significant association was detected in the miscellaneous subgroup under the dominant model (fixed-effects model: OR 5.69, 95% CI 4.70-6.88; P = 0.000) and overdominant model (random-effects model: OR 5.24, 95% CI 2.26-12.17; P = 0.000).

CONCLUSIONS

This meta-analysis indicates that TNF-α-308 G/A polymorphism is not a genetic risk factor for vitiligo.

Involvement of interferon-gamma genetic variants and intercellular adhesion molecule-1 in onset and progression of generalized vitiligo

Interferon-gamma (IFN-γ) is a paracrine inhibitor of melanocytes and genetic variability due to intron 1 polymorphisms in IFNG has been reported to be associated with increased risk for several autoimmune diseases. The aim of present study was to determine whether intron 1 +874A/T (rs2430561) and CA microsatellite (rs3138557) polymorphisms in IFNG are associated with generalized vitiligo (GV) susceptibility and expression of IFNG and intercellular adhesion molecule-1 (ICAM1) affects the disease onset and progression. Here we report that IFNG CA microsatellite but not +874A/T may be a genetic risk factor for GV; however, +874T allele plays a crucial role in increased expression of IFNG mRNA and protein levels which could affect the onset and progression of the disease. Active GV patients showed increased IFNG levels compared to stable GV patients. The genotype-phenotype analysis revealed that IFNG expression levels were higher in patients with +874 TT genotypes and 12 CA repeats. Patients with the early age of onset showed higher IFNG expression and female GV patients showed higher IFNG and ICAM1 expression implicating gender biasness and involvement of IFN-γ in early onset of the disease. Moreover, the increased IFN-γ levels in patients lead to increased ICAM1 expression, which could be a probable link between cytokines and T-cell involvement in pathogenesis of GV.

The role of tumor necrosis factor-α in the pathogenesis of vitiligo

Vitiligo is an acquired immune disorder of the skin characterized by the presence of white depigmented macules. Its immunopathogenesis is not completely understood, but inflammatory alterations in the skin microenvironment, and particularly increased expression of the cytokine tumor necrosis factor-α (TNFα), are thought to be essential regulators of melanocyte dysfunction and death. In this article we review the evidence that implicates TNFα in the pathogenesis of vitiligo, including studies on serum and tissue levels of TNFα, TNFα gene polymorphisms, in vitro studies, and therapeutic trials using TNFα inhibitors. TNFα emerges as a complex mediator with apparently conflicting roles in vitiligo.

Three new single nucleotide polymorphisms identified by a genome-wide association study in Korean patients with vitiligo

Genetic susceptibility is involved in the pathogenesis of vitiligo. Association studies with a whole genome-based approach instead of a single or a few candidate genes may be useful for discovering new susceptible genes. Although the etiology of non-segmental and segmental types is different, the association between gene polymorphisms and vitiligo has been reported, without defining types or in non-segmental type. Whole genome-based single nucleotide polymorphisms (SNPs) were examined in patients with non-segmental and segmental types of vitiligo using the Affymetrix GeneChip 500K mapping array, and 10 functional classes of significant SNPs were selected. Genotyping and data analysis of selected 10 SNPs was performed using real-time PCR. Genotype and allele frequencies were significantly different between both types of vitiligo and three of the target SNPs, DNAH5 (rs2277046), STRN3 (rs2273171), and KIAA1005 (rs3213758). A stronger association was suggested between the mutation in KIAA1005 (rs3213758) and the segmental type compared to the non-segmental type of vitiligo. DNAH5 (rs2277046), STRN3 (rs2273171), and KIAA1005 (rs3213758) may be new vitiligo-related SNPs in Korean patients, either non-segmental or segmental type.

Increased Tumor Necrosis Factor (TNF)-α and its promoter polymorphisms correlate with disease progression and higher susceptibility towards vitiligo

Tumor Necrosis Factor (TNF)-α, is a paracrine inhibitor of melanocytes, which plays a critical role in the pathogenesis of several autoimmune diseases including vitiligo, as abnormal immune responses have frequently been observed in vitiligo patients. Moreover, vitiligo patients show higher lesion levels of TNF-α. Genetic polymorphisms in the promoter region of TNF-α are involved in the regulation of its expression. The present study explores TNF-α promoter polymorphisms and correlates them with TNF-α transcript and protein levels in vitiligo patients and controls of Gujarat along with its effect on disease onset and progression. PCR-RFLP technique was used for genotyping of these polymorphisms in 977 vitiligo patients and 990 controls. TNF-α transcript and protein levels were measured by Real time PCR and ELISA respectively. The genotype and allele frequencies for the investigated polymorphisms were significantly associated with vitiligo patients. The study revealed significant increase in TNF-α transcript and protein levels in vitiligo patients compared to controls. In particular, haplotypes: AATCC, AACCT, AGTCT, GATCT, GATCC and AGCCT were found to increase the TNF-α levels in vitiligo patients. Analysis of TNF-α levels based on the gender and disease progression suggests that female patients and patients with active vitiligo had higher levels of TNF-α. Also, the TNF-α levels were high in patients with generalized vitiligo as compared to localized vitiligo. Age of onset analysis of the disease suggests that the haplotypes: AACAT, AACCT, AATCC and AATCT had a profound effect in the early onset of the disease. Moreover, the analysis suggests that female patients had an early onset of vitiligo. Overall, our results suggest that TNF-α promoter polymorphisms may be genetic risk factors for susceptibility and progression of the disease. The up-regulation of TNF-α transcript and protein levels in individuals with susceptible haplotypes advocates the crucial role of TNF-α in autoimmune pathogenesis of vitiligo.

A comparative study on efficacy of UVA1 vs. narrow-band UVB phototherapy in the treatment of vitiligo

BACKGROUND/PURPOSE

Narrow-band ultraviolet B (NB-UVB) is considered the most effective and safe initial treatment for moderate-to-severe vitiligo but phototoxicity and possible carcinogenicity are the reported side effects. Ultraviolet A1 (UVA1) phototherapy has overlapping biological effects to NB-UVB and is relatively free of side effects associated with other phototherapy regimens.

METHODS

Forty patients with vitiligo were included in this prospective, randomized controlled comparative clinical trial. Twenty patients received NB-UVB and 20 received UVA1 three times weekly for 12 weeks. The UVA1 group was divided into two subgroups. Ten patients received moderate and 10 received low dose of UVA1. Serum samples were collected before and after 36 sessions to assess soluble interleukin 2 receptor level. Patients were clinically evaluated before therapy then monthly according to Vitiligo Area Scoring Index (VASI) and Vitiligo European Task Force (VETF) scores. In addition, extent of response was determined by a blinded dermatologist comparing before and after therapy photographs. Pattern of response and side effects were recorded.

RESULTS

NB-UVB was superior to UVA1 with a significant difference in blinded dermatological assessment (P<0.001), percentage change in VASI score (P<0.001) and percentage change in VETF area score (P=0.001). No significant difference in side effects was observed between both groups. Comparing UVA1 subgroups, better response in moderate-dose group was found as regard to percentage change in VASI (P<0.001) and percentage change in VETF area score (P=0.001), while no significant difference was found in blinded dermatological assessment (P=0.121).

CONCLUSION

NB-UVB phototherapy remains to be an effective and safe therapeutic option in vitiligo. Response to UVA1 in vitiligo seems to be dose dependent and seems to be of limited value in treatment of vitiligo as a monotherapy. Further studies combining it with other lines of therapy such as systemic steroids may prove beneficial.

Tumor necrosis factor-α -308G/A polymorphism is associated with active vitiligo vulgaris in a northeastern Mexican population

Vitiligo is a skin disease characterized by depigmentation. Its etiopathogenesis is unclear, but it has been associated with autoimmune processes. Gene polymorphisms in the tumor necrosis factor-α (TNF-α) have been associated with several imflammatory diseases. In particular, the -308G/A polymorphism in the gene promoter region has been reported to be associated with increased plasma levels of TNF-α and with an increased risk to develop autoimmune diseases. To date, this polymorphism has not been associated with vitiligo. To assess a possible association between the TNF-α -308G/A and vitiligo vulgaris (VV), 198 vitiligo patients and 395 control subjects were recruited for the study. A complete demographic and clinical profile of each case was registered to analyze the possible risk factors of vitiligo. Genomic DNA isolated from peri pheral blood was subjected to PCR-RFLP for genotyping of the TNF-α -308G/A polymorphism. Causal associations were determined by χ(2) test and their respective OR was assessed in a 2×2 contingency table. When population variables of type of vitiligo, gender, age of disease onset, and active disease status were considered, an association between active VV and the TNF-α GA genotype was found (P=0.0295, OR=2.0; 95% CI 1.01-3.93). All other variables were irrelevant to vitiligo. Our data suggest a possible association between the TNF-α -308 GA genotype and the active form of VV in a Mexican population.

Immunopathogenesis of vitiligo

Vitiligo is a common depigmenting disorder which may have devastating psychological and social consequences and is characterized by the presence of circumscribed white macules in the skin due to the destruction of melanocytes in the epidermis. Various hypotheses have been proposed to explain the pathomechanisms involved in this disease, and studies have shown the participation of autoimmune processes in the pathogenesis of vitiligo. Cellular and humoral immunities have been implicated in the development of vitiligo and their role continues to be investigated. Peripheral blood and skin biopsies of patients with vitiligo show that T-cells, mononuclear cells, various pro-inflammatory cytokines, and auto-antibodies can damage melanocytes. Further research is required to determine whether autoimmunity is the main mechanism of vitiligo or only a consequence.

Role of interleukin-17 in the pathogenesis of vitiligo

BACKGROUND

Skewing of the immune response towards T helper (Th)1 or Th17 and away from regulatory T cells (Tregs) and Th2 cells may be responsible for the development and progression of autoimmune disease. An autoimmune theory has been proposed in the pathogenesis of vitiligo. No previous reports have investigated alterations in IL-17 produced by Th17 cells in lesional skin in vitiligo.

AIM

To investigate the role of IL-17 in the pathogenesis of vitiligo by assessing its levels in lesional skin and serum of patients with vitiligo compared with controls.

METHODS

In total, 30 patients with vitiligo and 20 controls matched for age and gender were enrolled in the study. Serum and tissue IL-17 levels were measured by ELISA and compared between both groups for correlations with age, gender, family history, disease duration, activity of vitiligo and percentage of involved body surface area.

RESULTS

A significant difference between patients and healthy controls was found for both serum and tissue IL-17 levels (P<0.001 for both). Significant positive correlations were found between disease duration and IL-17 level in both serum (r=0.42, P=0.02) and lesional skin (r=0.45, P<0.015); between extent of vitiligo and IL-17 levels in both serum (r=0.65, P<0.001) and skin (r=0.48, P<0.05); and between the serum and the tissue IL-17 levels in patients with vitiligo (r=0.54, P=0.002).

CONCLUSIONS

Multiple factors have been implicated in the pathogenesis of vitiligo. The increased levels of IL-17 we found in serum and lesional skin suggest an important role for this cytokine in the pathogenesis of vitiligo.

Comprehensive association analysis of candidate genes for generalized vitiligo supports XBP1, FOXP3, and TSLP

We previously carried out a genome-wide association study of generalized vitiligo (GV) in non-Hispanic whites, identifying 13 confirmed susceptibility loci. In this study, we re-analyzed the genome-wide data set (comprising 1,392 cases and 2,629 controls) to specifically test association of all 33 GV candidate genes that have previously been suggested for GV, followed by meta-analysis incorporating both current and previously published data. We detected association of three of the candidate genes tested: TSLP (rs764916, P=3.0E-04, odds ratio (OR)=1.60; meta-P for rs3806933=3.1E-03), XBP1 (rs6005863, P=3.6E-04, OR=1.17; meta-P for rs2269577=9.5E-09), and FOXP3 (rs11798415, P=5.8E-04, OR=1.19). Association of GV with CTLA4 (rs12992492, P=5.9E-05, OR=1.20; meta-P for rs231775=1.0E-04) seems to be secondary to epidemiological association with other concomitant autoimmune diseases. Within the major histocompatibility complex (MHC), at 6p21.33, association with TAP1-PSMB8 (rs3819721, P=5.2E-06) seems to derive from linkage disequilibrium with major primary signals in the MHC class I and class II regions.