Association of generalized vitiligo with MHC class II loci in patients from the Indian subcontinent

Paraoxonase 1 (PON1) gene Q192R polymorphism in patients with vitiligo

Background/Aim: Vitiligo is a prevalent inflammatory illness that can affect the skin and mucosal surfaces and is characterized by patchy loss of skin pigmentation. Paraoxonase1 (PON1) is an esterase enzyme with antioxidant properties that binds to high-density lipoproteins. We examined whether the PON1 gene Q192R polymorphism is a risk factor for vitiligo among Turkish people. Methods: The study included 70 controls and 60 vitiligo cases. Polymerase chain reaction and the restriction fragment length polymorphism technique were used to genotype the PON1 gene Q192R polymorphism. Results: PON1 gene Q192R genotype distribution was 66.7% QQ, 33.3% QR, and 0% RR in the vitiligo and 81.4% QQ, 18.6% QR, and 0% RR in the control (P = 0.05). When vitiligo patients were compared with controls, the prevalence of the PON1 QR genotype was substantially higher and was linked to a 2.19-fold greater risk of developing vitiligo (odds ratio: 2.19, 95% confidence interval (CI): 0.97–4.91). Conclusion: These findings imply that Q192R polymorphisms in the PON-1 gene may be linked to vitiligo in the Turkish population. The PON1 QR genotype may be a major genetic risk factor for vitiligo susceptibility and progression. Further studies with larger populations should more thoroughly clarify the association.

V-set domain containing T-cell activation inhibitor-1 (VTCN1): A potential target for the treatment of autoimmune diseases

Autoimmunity eventuates when the immune system attacks self-molecules as a result of the breakdown in immune tolerance. Targeting autoimmune diseases via immunomodulation has become an essential strategy in today's era. A B7 superfamily member immune checkpoint, the V-set domain containing T-cell activation inhibitor-1 (VTCN1), also known as B7-H4, B7S1, and B7x, is involved in negatively regulating T-cell activation. VTCN1 transcript has been reported in various lymphoid and non-lymphoid tissues, but its protein expression is restricted, indicating its translational regulation. Dysregulation of VTCN1 has resulted in the exacerbation of various autoimmune diseases. Moreover, increased soluble form of VTCN1 in the patient's sera positively correlates with the disease progression and severity. The current review summarizes all the reports till date, unfolding the role of VTCN1 in various autoimmune diseases and its therapeutic potential.

Fine Mapping Analysis of the MHC Region to Identify Variants Associated With Chinese Vitiligo and SLE and Association Across These Diseases

The important role of MHC in the pathogenesis of vitiligo and SLE has been confirmed in various populations. To map the most significant MHC variants associated with the risk of vitiligo and SLE, we conducted fine mapping analysis using 1117 vitiligo cases, 1046 SLE cases and 1693 healthy control subjects in the Han-MHC reference panel and 1000 Genomes Project phase 3. rs113465897 (P=1.03×10^-13, OR=1.64, 95%CI =1.44–1.87) and rs3129898 (P=4.21×10^-17, OR=1.93, 95%CI=1.66–2.25) were identified as being most strongly associated with vitiligo and SLE, respectively. Stepwise conditional analysis revealed additional independent signals at rs3130969(p=1.48×10^-7, OR=0.69, 95%CI=0.60–0.79), HLA-DPB1*03:01 (p=1.07×10^-6, OR=1.94, 95%CI=1.49–2.53) being linked to vitiligo and HLA-DQB1*0301 (P=4.53×10^-7, OR=0.62, 95%CI=0.52-0.75) to SLE. Considering that epidemiological studies have confirmed comorbidities of vitiligo and SLE, we used the GCTA tool to analyse the genetic correlation between these two diseases in the HLA region, the correlation coefficient was 0.79 (P=5.99×10^-10, SE=0.07), confirming their similar genetic backgrounds. Our findings highlight the value of the MHC region in vitiligo and SLE and provide a new perspective for comorbidities among autoimmune diseases.

Variations in TAP1 and PSMB9 Genes Involved in Antigen Processing and Presentation Increase the Risk of Vitiligo in the Saudi Community

Background

The antigen processing 1 (TAP1) and proteasome 20S subunit beta 9 (PSMB9) genes are associated with strong susceptibility to many autoimmune diseases. Here, we explored whether TAP1/PSMB9 genetic variants, individually or combined, affected susceptibility to the complex, autoimmune-based skin disorder vitiligo.

Methods

Samples of genomic DNA from buccal cells of 172 patients with vitiligo and 129 healthy controls were analyzed using TaqMan™ genotyping assays for the TAP1 rs1135216 (A>G) and PSMB9 rs17587 (A>G) single nucleotide polymorphisms (SNPs). SNPStats software (https://www.snpstats.net) was utilized to choose the best interactive inheritance mode for selected SNPs.

Results

The genotype frequencies for the TAP1 rs1135216 and PSMB9 rs17587 SNPs were in Hardy-Weinberg equilibrium for cases (P= 0.11 and P= 0.10, respectively) but not for controls (P< 0.05). The TAP1 rs1135216 (D637G) and PSMB9 rs17587 (R60H) SNPs increased the risk of vitiligo four-fold and two-fold, respectively (odds ratio [OR]= 4.6; 95% confidence interval [CI], 3.2-6.5; P< 0.0001 and OR= 2.2; 95% CI, 1.5-3.1; P< 0.0001). The recessive model (G/G-D/G versus D/D) and the codominant model (R/R versus R/H) were the best models of inheritance for the rs113526 and rs17587 SNPs, respectively (OR= 16.4; 95% CI, 2.0-138; P= 0.0006 and OR= 1.7; 95% CI, 0.3-1.8; P= 0.013). Vulgaris, focal vulgaris, and acryl/acrofacial were the most common vitiligo subtypes in our sample (51%, 21%, and 19%, respectively). Heterozygous rs113526 (637D/G) and rs17587 (60R/H) were the most common genotypes in most vitiligo subtypes. The heterozygous 637D/G genotype and the 637G variant allele were significantly more common in patients with active disease than in patients with stable disease (P= 0.000052 and P= 0.0063, respectively).

Conclusion

Our findings suggest a crucial role for TAP1 rs1135216 and PSMB9 rs17587 in the risk and progression of vitiligo in the Saudi community. Genomic analyses are needed to identify more candidate genes and more genetic variants associated with vitiligo.

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

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

A Concise Review on the Role of Endoplasmic Reticulum Stress in the Development of Autoimmunity in Vitiligo Pathogenesis

Vitiligo is characterized by circumscribed depigmented macules in the skin resulting due to the autoimmune destruction of melanocytes from the epidermis. Both humoral as well as cell-mediated autoimmune responses are involved in melanocyte destruction. Several studies including ours have established that oxidative stress is involved in vitiligo onset, while autoimmunity contributes to the disease progression. However, the underlying mechanism involved in programing the onset and progression of the disease remains a conundrum. Based on several direct and indirect evidences, we suggested that endoplasmic reticulum (ER) stress might act as a connecting link between oxidative stress and autoimmunity in vitiligo pathogenesis. Oxidative stress disrupts cellular redox potential that extends to the ER causing the accumulation of misfolded proteins, which activates the unfolded protein response (UPR). The primary aim of UPR is to resolve the stress and restore cellular homeostasis for cell survival. Growing evidences suggest a vital role of UPR in immune regulation. Moreover, defective UPR has been implicated in the development of autoimmunity in several autoimmune disorders. ER stress-activated UPR plays an essential role in the regulation and maintenance of innate as well as adaptive immunity, and a defective UPR may result in systemic/tissue level/organ-specific autoimmunity. This review emphasizes on understanding the role of ER stress-induced UPR in the development of systemic and tissue level autoimmunity in vitiligo pathogenesis and its therapeutics.

Variations in TAP1 and PSMB9 Genes Involved in Antigen Processing and Presentation Increase the Risk of Vitiligo in the Saudi Community

BACKGROUND

The antigen processing 1 (TAP1) and proteasome 20S subunit beta 9 (PSMB9) genes are associated with strong susceptibility to many autoimmune diseases. Here, we explored whether TAP1/PSMB9 genetic variants, individually or combined, affected susceptibility to the complex, autoimmune-based skin disorder vitiligo.

METHODS

Samples of genomic DNA from buccal cells of 172 patients with vitiligo and 129 healthy controls were analyzed using TaqMan™ genotyping assays for the TAP1 rs1135216 (A>G) and PSMB9 rs17587 (A>G) single nucleotide polymorphisms (SNPs). SNPStats software (https://www.snpstats.net) was utilized to choose the best interactive inheritance mode for selected SNPs.

RESULTS

The genotype frequencies for the TAP1 rs1135216 and PSMB9 rs17587 SNPs were in Hardy-Weinberg equilibrium for cases (P= 0.11 and P= 0.10, respectively) but not for controls (P< 0.05). The TAP1 rs1135216 (D637G) and PSMB9 rs17587 (R60H) SNPs increased the risk of vitiligo four-fold and two-fold, respectively (odds ratio [OR]= 4.6; 95% confidence interval [CI], 3.2-6.5; P< 0.0001 and OR= 2.2; 95% CI, 1.5-3.1; P< 0.0001). The recessive model (G/G-D/G versus D/D) and the codominant model (R/R versus R/H) were the best models of inheritance for the rs113526 and rs17587 SNPs, respectively (OR= 16.4; 95% CI, 2.0-138; P= 0.0006 and OR= 1.7; 95% CI, 0.3-1.8; P= 0.013). Vulgaris, focal vulgaris, and acryl/acrofacial were the most common vitiligo subtypes in our sample (51%, 21%, and 19%, respectively). Heterozygous rs113526 (637D/G) and rs17587 (60R/H) were the most common genotypes in most vitiligo subtypes. The heterozygous 637D/G genotype and the 637G variant allele were significantly more common in patients with active disease than in patients with stable disease (P= 0.000052 and P= 0.0063, respectively).

CONCLUSION

Our findings suggest a crucial role for TAP1 rs1135216 and PSMB9 rs17587 in the risk and progression of vitiligo in the Saudi community. Genomic analyses are needed to identify more candidate genes and more genetic variants associated with vitiligo.

The Role of MicroRNAs in Vitiligo: Regulators and Therapeutic Targets

Vitiligo is an acquired skin disorder clinically characterized by the progressive appearance of white maculae due to a loss of functioning epidermal melanocytes. Studies have shown that microRNAs (miRNAs) modulate cellular differentiation, proliferation and apoptosis, including immune cell and melanocyte development and functions. The role of miRNAs in the pathogenesis of several immune-related diseases has been explored. Novel approaches to target miRNAs have recently emerged allowing modulation of miRNAs levels in diverse pathological processes, thus making them promising targets for molecular-based diagnostics and therapy. Here, we report the present status of research on miRNAs expression and functional alterations in vitiligo, in order to more fully understand the role of these molecules in vitiligo pathology.

The Genetic Basis of Vitiligo

Vitiligo is a complex disease in which autoimmune destruction of epidermal melanocytes results in patches of depigmented white skin. Vitiligo has an estimated prevalence of about 0.2-2% in different populations and approximately 0.4% in the European-derived white (EUR) population. The fraction of disease risk attributable to genetic variation, termed heritability, is high, with estimates from family studies in EUR of 0.75-0.83 and from SNP based studies estimated at 0.78. About 70% of genetic risk comes from common genetic variants and about 30% from rare genetic variants. Through candidate gene, genomewide linkage, and genomewide association studies, over 50 vitiligo susceptibility loci have been discovered. These have been combined into a vitiligo polygenic risk score, which has allowed various aspects of vitiligo genetic architecture in the EUR population to be better understood. Vitiligo has thus proved to be a particularly tractable model for investigation of complex disease genetic architecture. Here, we summarize progress to date including dissection of heritability, discovery of vitiligo susceptibility loci through candidate gene, genomewide linkage, and genomewide association studies, relationships to other autoimmune diseases, polygenic architecture of vitiligo risk, vitiligo triggering, and disease onset, and provide suggestions for future directions.

Genetics of Vitiligo

Vitiligo reflects simultaneous contributions of multiple genetic risk factors and environmental triggers. Genomewide association studies have discovered approximately 50 genetic loci contributing to vitiligo risk. At many vitiligo susceptibility loci, the relevant genes and DNA sequence variants are identified. Many encode proteins involved in immune regulation, several play roles in cellular apoptosis, and others regulate functions of melanocytes. Although many of the specific biologic mechanisms need elucidation, it is clear that vitiligo is an autoimmune disease involving a complex relationship between immune system programming and function, aspects of the melanocyte autoimmune target, and dysregulation of the immune response.

Association and expression of the antigen-processing gene PSMB8, coding for low-molecular-mass protease 7, with vitiligo in North India: case-control study

BACKGROUND

Vitiligo is a multifactorial, autoimmune, depigmenting disorder of the skin where aberrant presentation of autoantigens may have a role.

OBJECTIVES

To study the association of two antigen-processing genes, PSMB8 and PSMB9, with vitiligo.

METHODS

In total 1320 cases of vitiligo (1050 generalized and 270 localized) and 752 healthy controls were studied for the PSMB9 exon 3 G/A single-nucleotide polymorphism (SNP), PSMB8 exon 2 C/A SNP and PSMB8 intron 6 G/T SNP at site 37 360 using polymerase chain reaction (PCR)-restriction fragment length polymorphism. Real-time PCR was used for transcriptional expression of PSMB8 and cytokines. Expression of ubiquitinated proteins and phosphorylated-p38 (P-p38) was studied by Western blotting.

RESULTS

Significant increases in PSMB8 exon 2 allele A (P < 2.07 × 10^-6 , odds ratio 1·93) and genotypes AA (P < 1.03 × 10^-6 , odds ratio 2·51) and AC (P < 1.29 × 10^-6 , odds ratio 1·63) were observed in patients with vitiligo. Interferon-γ stimulation induced lower expression of PSMB8 in peripheral blood mononuclear cells of cases compared with controls, suggesting impaired antigen processing, which was confirmed by accumulation of ubiquitinated proteins in both lesional and nonlesional skin of patients with vitiligo. Expression of proinflammatory cytokines - interleukin (IL)-6, IL-1β and IL-8 - was higher in the lesional skin. P-p38 expression was variable but correlated with the amount of ubiquitinated proteins in the lesional and nonlesional skin, suggesting that the inflammatory cytokine responses in lesional skin could be a result of both P-p38-dependent and -independent pathways.

CONCLUSIONS

The PSMB8 exon 2 SNP is significantly associated with vitiligo. Accumulation of ubiquitinated proteins in skin of cases of vitiligo suggests their aberrant processing, which may promote the development of the disease.

A case-control study on association of proteasome subunit beta 8 (PSMB8) and transporter associated with antigen processing 1 (TAP1) polymorphisms and their transcript levels in vitiligo from Gujarat

BACKGROUND

Autoimmunity has been implicated in the destruction of melanocytes from vitiligo skin. Major histocompatibility complex (MHC) class-II linked genes proteasome subunit beta 8 (PSMB8) and transporter associated with antigen processing 1 (TAP1), involved in antigen processing and presentation have been reported to be associated with several autoimmune diseases including vitiligo.

OBJECTIVES

To explore PSMB8 rs2071464 and TAP1 rs1135216 single nucleotide polymorphisms and to estimate the expression of PSMB8 and TAP1 in patients with vitiligo and unaffected controls from Gujarat.

METHODS

PSMB8 rs2071464 polymorphism was genotyped using polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP) and TAP1 rs1135216 polymorphism was genotyped by amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) in 378 patients with vitiligo and 509 controls. Transcript levels of PSMB8 and TAP1 were measured in the PBMCs of 91 patients and 96 controls by using qPCR. Protein levels of PSMB8 were also determined by Western blot analysis.

RESULTS

The frequency of 'TT' genotype of PSMB8 polymorphism was significantly lowered in patients with generalized and active vitiligo (p = 0.019 and p = 0.005) as compared to controls suggesting its association with the activity of the disease. However, TAP1 polymorphism was not associated with vitiligo susceptibility. A significant decrease in expression of PSMB8 at both transcript level (p = 0.002) as well as protein level (p = 0.0460) was observed in vitiligo patients as compared to controls. No significant difference was observed between patients and controls for TAP1 transcripts (p = 0.553). Interestingly, individuals with the susceptible CC genotype of PSMB8 polymorphism showed significantly reduced PSMB8 transcript level as compared to that of CT and TT genotypes (p = 0.009 and p = 0.003 respectively).

CONCLUSIONS

PSMB8 rs2071464 was associated with generalized and active vitiligo from Gujarat whereas TAP1 rs1135216 showed no association. The down-regulation of PSMB8 in patients with risk genotype 'CC' advocates the vital role of PSMB8 in the autoimmune basis of vitiligo.

Possible patterns of epidermal melanocyte disappearance in nonsegmental vitiligo: a clinicopathological study

BACKGROUND

The depigmentation of vitiligo results in a progressive and chronic melanocyte loss with rare melanocytes occasionally remaining in the epidermis or the hair follicle reservoirs. Destruction by immune infiltrates in close contact with melanocytes within microvesicles and/or detachment of melanocytes followed by their transepidermal elimination should be regarded as possible mechanisms of chronic loss of pigment cells.

OBJECTIVES

To assess the frequency of these two histological findings and to establish a direct correlation with clinical features.

METHODS

This was a prospective observational study that took place over 1 year. Each patient received a standardized evaluation that included daylight and Wood's lamp examinations, pictures, biopsies performed on the marginal area, and histological and immunohistological studies. A second examination to assess the activity of the lesions was performed 1 year after inclusion in the study. Clinical changes associated with microvesicles were compared with those associated with detached melanocytes from the basal layer.

RESULTS

This study included 50 patients. The histological findings were classified as inflammatory with isolated microvesicles (29 cases), noninflammatory with only detached melanocytes from the basal layer (12 cases) and a combination of coexisting microvesicles and detached melanocytes (six cases). Correlations were obtained between the histological findings and clinical features (aspect and activity of the lesions) and E-cadherin expression.

CONCLUSIONS

Our data suggest the existence of two patterns of melanocyte disappearance in nonsegmental vitiligo.

Association of neuropeptide Y (NPY), interleukin-1B (IL1B) genetic variants and correlation of IL1B transcript levels with vitiligo susceptibility

BACKGROUND

Vitiligo is a depigmenting disorder resulting from loss of functional melanocytes in the skin. NPY plays an important role in induction of immune response by acting on a variety of immune cells. NPY synthesis and release is governed by IL1B. Moreover, genetic variability in IL1B is reported to be associated with elevated NPY levels.

OBJECTIVES

Aim of the present study was to explore NPY promoter -399T/C (rs16147) and exon2 +1128T/C (rs16139) polymorphisms as well as IL1B promoter -511C/T (rs16944) polymorphism and to correlate IL1B transcript levels with vitiligo.

METHODS

PCR-RFLP method was used to genotype NPY -399T/C SNP in 454 patients and 1226 controls; +1128T/C SNP in 575 patients and 1279 controls and IL1B -511C/T SNP in 448 patients and 785 controls from Gujarat. IL1B transcript levels in blood were also assessed in 105 controls and 95 patients using real-time PCR.

RESULTS

Genotype and allele frequencies for NPY -399T/C, +1128T/C and IL1B -511C/T SNPs differed significantly (p<0.0001, p<0.0001; p = 0.0161, p = 0.0035 and p<0.0001, p<0.0001) between patients and controls. 'TC' haplotype containing minor alleles of NPY polymorphisms was significantly higher in patients and increased the risk of vitiligo by 2.3 fold (p<0.0001). Transcript levels of IL1B were significantly higher, in patients compared to controls (p = 0.0029), in patients with active than stable vitiligo (p = 0.015), also in female patients than male patients (p = 0.026). Genotype-phenotype correlation showed moderate association of IL1B -511C/T polymorphism with higher IL1B transcript levels. Trend analysis revealed significant difference between patients and controls for IL1B transcript levels with respect to different genotypes.

CONCLUSION

Our results suggest that NPY -399T/C, +1128T/C and IL1B -511C/T polymorphisms are associated with vitiligo and IL1B -511C/T SNP influences its transcript levels leading to increased risk for vitiligo in Gujarat population. Up-regulation of IL1B transcript in patients advocates its possible role in autoimmune pathogenesis of vitiligo.

Analysis of oxidative stress status, catalase and catechol-O-methyltransferase polymorphisms in Egyptian vitiligo patients

Vitiligo is the most common depigmentation disorder of the skin. Oxidative stress is implicated as one of the probable events involved in vitiligo pathogenesis possibly contributing to melanocyte destruction. Evidence indicates that certain genes including those involved in oxidative stress and melanin synthesis are crucial for development of vitiligo. This study evaluates the oxidative stress status, the role of catalase (CAT) and catechol-O-Methyltransferase (COMT) gene polymorphisms in the etiology of generalized vitiligo in Egyptians. Total antioxidant capacity (TAC) and malondialdehyde (MDA) levels as well as CAT exon 9 T/C and COMT 158 G/A polymorphisms were determined in 89 patients and 90 age and sex-matched controls. Our results showed significantly lower TAC along with higher MDA levels in vitiligo patients compared with controls. Meanwhile, genotype and allele distributions of CAT and COMT polymorphisms in cases were not significantly different from those of controls. Moreover, we found no association between both polymorphisms and vitiligo susceptibility. In conclusion, the enhanced oxidative stress with the lack of association between CAT and COMT polymorphisms and susceptibility to vitiligo in our patients suggest that mutations in other genes related to the oxidative pathway might contribute to the etiology of generalized vitiligo in Egyptian population.

Association of the 389 C/T polymorphism of the catalase gene with susceptibility to vitiligo: a meta-analysis

BACKGROUND

The 389 C/T polymorphism in the catalase gene, CAT, has been reported to be associated with the risk of vitiligo.

AIM

To evaluate the association of the CAT 389 C/T polymorphism with susceptibility to vitiligo.

METHODS

We undertook a literature search and included the relevant studies passing the selection criteria. After the relevant data were extracted from each study, we statistically analysed the strength of association between the CAT gene and vitiligo risk.

RESULTS

In total, 7 relevant studies were identified, comprising 1531 patients with vitiligo and 1608 controls. The genotype distribution in the controls of all studies complied with Hardy-Weinberg equilibrium. After pooling all studies, the results indicated that the 389 C/T polymorphisms in CAT were not associated with the risk of vitiligo in Asians and Turks; however the CT genotype might be a genetic risk factor for susceptibility to vitiligo (OR = 1.77, 95% CI 1.30-2.43, P < 0.001) and the CC genotype might decrease the risk of vitiligo (OR = 0.63, 95% CI 0.47-0.86, P < 0.01) in western Europeans.

CONCLUSIONS

The 389 C/T polymorphisms in the CAT gene may be associated with vitiligo in western Europeans. Further studies with larger sample sizes are warranted to confirm our findings.

Modern vitiligo genetics sheds new light on an ancient disease

Vitiligo is a complex disorder in which autoimmune destruction of melanocytes results in white patches of skin and overlying hair. Over the past several years, extensive genetic studies have outlined a biological framework of vitiligo pathobiology that underscores its relationship to other autoimmune diseases. This biological framework offers insight into both vitiligo pathogenesis and perhaps avenues towards more effective approaches to treatment and even disease prevention.

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.

Association of NLRP1 genetic variants and mRNA overexpression with generalized vitiligo and disease activity in a Gujarat population

BACKGROUND

It has been suggested that NLRP1 is involved in susceptibility to a wide range of autoimmune diseases including generalized vitiligo (GV). Genetic polymorphisms in the gene encoding NLRP1 (previously known as NALP1) have previously been shown to be associated with GV and there is speculation about their involvement in the regulation of NLRP1 expression.

OBJECTIVES

To explore NLRP1 polymorphisms and investigate their association with NLRP1 mRNA expression and disease activity in patients with GV.

METHODS

Polymerase chain reaction (PCR)-restriction fragment length polymorphism and TaqMan single nucleotide polymorphism (SNP) genotyping techniques were used to genotype NLRP1 A/G (rs2670660), T/C (rs6502867) and A/T (rs12150220) polymorphisms in 537 patients with GV and 645 controls in Gujarat. NLRP1 mRNA levels were measured in the whole blood of 122 patients with GV and 175 controls using real-time PCR.

RESULTS

The NLRP1 rs2670660 and rs6502867 polymorphisms were found to be in significant association with GV, minor alleles of these SNPs being prevalent in active cases of GV. The rs12150220 polymorphism was found have a marginal association with GV. The frequency of susceptible haplotype 'GCT' was significantly higher in patients with GV and increased the risk of vitiligo twofold. A significant increase in NLRP1 mRNA expression was observed in patients with GV and patients with active GV. NLRP1 mRNA expression was increased in patients with GV with the susceptible GG (rs2670660) and CC (rs6502867) genotypes. Patients with the susceptible GG (rs2670660) and CC (rs6502867) genotypes had early age of onset of GV. Moreover, patients in the age at onset group of 1-20 years showed increased expression of NLRP1 mRNA compared with the older age groups. Female patients showed a significant increase in NLRP1 mRNA and early age at onset of GV compared with male patients.

CONCLUSIONS

Our results suggest that NLRP1 rs2670660 and rs6502867 polymorphisms may be genetic risk factors for susceptibility to and progression of GV. The upregulation of NLRP1 mRNA in patients with susceptible genotypes advocates the crucial role of NLRP1 in GV.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Decreased regulatory T-cells and CD4(+) /CD8(+) ratio correlate with disease onset and progression in patients with generalized vitiligo

The aim of present study was to evaluate CD4(+) /CD8(+) ratio and CD4(+) CD25(hi) FoxP3(+) Tregs in GV patients with reference to their effect on disease onset and progression. Flow cytometry was used for determination of CD4(+) /CD8(+) ratio and Tregs in 82 patients and 50 controls. CD8(+) T-cell counts were significantly higher in GV patients as compared with controls (p = 0.003). Active GV patients showed higher CD8(+) T-cell counts compared with stable GV patients (p = 0.001). The CD4(+) /CD8(+) ratio decreased significantly in patients as compared with controls (p = 0.001). Moreover, the ratio in active GV patients significantly lowered as compared with stable GV patients (p = 0.002). Significant decrease in Treg cell percentage and counts in GV patients was observed compared with controls (p = 0.009, p = 0.008) with significant reduction in FoxP3 expression (p = 0.024). Treg cell percentage and counts were significantly decreased in active GV patients compared with stable GV patients (p = 0.007, p = 0.002). Our results suggest that an imbalance of CD4(+) /CD8(+) ratio and natural Tregs in frequency and function might be involved in the T-cell mediated pathogenesis of GV and its progression.

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

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