The association between endothelin-1 gene polymorphisms and susceptibility to vitiligo in a Korean population

Melanocyte-keratinocyte cross-talk in vitiligo

Vitiligo is a common acquired pigmentary disorder that presents as progressive loss of melanocytes from the skin. Epidermal melanocytes and keratinocytes are in close proximity to each other, forming a functional and structural unit where keratinocytes play a pivotal role in supporting melanocyte homeostasis and melanogenesis. This intimate relationship suggests that keratinocytes might contribute to ongoing melanocyte loss and subsequent depigmentation. In fact, keratinocyte dysfunction is a documented phenomenon in vitiligo. Keratinocyte apoptosis can deprive melanocytes from growth factors including stem cell factor (SCF) and other melanogenic stimulating factors which are essential for melanocyte function. Additionally, keratinocytes control the mobility/stability phases of melanocytes via matrix metalloproteinases and basement membrane remodeling. Hence keratinocyte dysfunction may be implicated in detachment of melanocytes from the basement membrane and subsequent loss from the epidermis, also potentially interfering with repigmentation in patients with stable disease. Furthermore, keratinocytes contribute to the autoimmune insult in vitiligo. Keratinocytes express MHC II in perilesional skin and may present melanosomal antigens in the context of MHC class II after the pigmented organelles have been transferred from melanocytes. Moreover, keratinocytes secrete cytokines and chemokines including CXCL-9, CXCL-10, and IL-15 that amplify the inflammatory circuit within vitiligo skin and recruit melanocyte-specific, skin-resident memory T cells. In summary, keratinocytes can influence vitiligo development by a combination of failing to produce survival factors, limiting melanocyte adhesion in lesional skin, presenting melanocyte antigens and enhancing the recruitment of pathogenic T cells.

Patho-immunological mechanisms of vitiligo: the role of the innate and adaptive immunities and environmental stress factors

Epidermal melanocyte loss in vitiligo, triggered by stresses ranging from trauma to emotional stress, chemical exposure or metabolite imbalance, to the unknown, can stimulate oxidative stress in pigment cells, which secrete damage-associated molecular patterns that then initiate innate immune responses. Antigen presentation to melanocytes leads to stimulation of autoreactive T-cell responses, with further targeting of pigment cells. Studies show a pathogenic basis for cellular stress, innate immune responses and adaptive immunity in vitiligo. Improved understanding of the aetiological mechanisms in vitiligo has already resulted in successful use of the Jak inhibitors in vitiligo. In this review, we outline the current understanding of the pathological mechanisms in vitiligo and locate loci to which therapeutic attack might be directed.

ZMIZ1 promotes the proliferation and migration of melanocytes in vitiligo

Genome wide association studies have revealed that the zinc finger MIZ-type containing 1 (ZMIZ1) is involved in the pathogenesis of vitiligo; however, the underlying mechanism remains unclear. The present study aimed to investigate the effects of ZMIZ1 on the proliferation, apoptosis and migration of the human melanocyte cell lines PIG1 and PIG3V. ZMIZ1 overexpression and knockdown PIG1 and PIG3V cell models were established by lentivirus infection, and the effects of ZMIZ1 on cell proliferation and apoptosis were determined using an MTT assay and flow cytometry, respectively. Furthermore, the expression levels of proliferation- and apoptosis-associated proteins were analyzed using western blotting. Additionally, Transwell assays were performed to determine the effect of ZMIZ1 on the migration of PIG1 and PIG3V cells. Finally, the effect of ZMIZ1 on cytoskeletal remodeling in PIG1 and PIG3V cells was analyzed using immunocytochemistry. The overexpression of ZMIZ1 promoted the proliferation and inhibited the apoptosis of PIG1 and PIG3V cells, whereas the genetic knockdown of ZMIZ1 resulted in the opposite effects. Furthermore, ZMIZ1 overexpression increased the migration, whereas the knockdown of ZMIZ1 inhibited the migration and altered remodeling of the actin cytoskeleton in PIG1 and PIG3V cells. In conclusion, the results of the present study suggest that ZMIZ1 regulates the proliferation, apoptosis and migration of PIG1 and PIG3V cells, and indicate that ZMIZ1 may serve as a potential therapeutic target for vitiligo.

The Evaluation of Endothelin-1 and Endothelin Receptor Type A Gene Polymorphisms in Patients with Vitiligo

Background:

Endothelin-1 (EDN1) and EDN receptor type A (EDNRA) are implicated in melanocyte functions.

Aim and Objectives:

This study examines the role of EDN1 (G5665T and T-1370G) and EDNRA (C + 70G and G-231A) polymorphisms as a risk factor for vitiligo, and evaluates the relationship between genotypes and clinical characteristics of vitiligo patients.

Materials and Methods:

We analyzed genotype/allele distributions of EDN1 and EDNRA polymorphisms in 100 patients with vitiligo and 185 healthy controls by real-time polymerase chain reaction.

Results:

There was no notable risk for vitiligo afflicted by studied polymorphisms. However, the presence of EDNRA +70 variant G allele was found to be related with decreased risk for development of generalized type of vitiligo (odds ratio [OR]: 0.42, 95% confidence interval [CI] = 0.21–0.86, p_corr = 0.03) and showed protective effect against associated diseases seen in vitiligo (OR: 0.49, 95% CI = 0.27–0.88, p_corr = 0.034). Haplotype analysis demonstrated a strong (disequilibrium coefficient = 0.73, r² = 0.405) linkage disequilibrium between EDN1 G5665T and T-1370G polymorphisms. The EDN1 5665/-1330 TT haplotype was over represented significantly in controls than in patients (P = 0.04).

Conclusion:

The studied polymorphisms do not seem to be a major risk for vitiligo. Haplotype analysis denoting protective effects against vitiligo may indicate an indirect interaction in the course of vitiligo. In addition, EDNRA + 70 polymorphism is protective against generalized type of vitiligo and associated diseases.

The evaluation of endothelin 1 (EDN1) and endothelin receptor type A (EDNRA) gene polymorphisms in Hashimoto's thyroiditis

PURPOSE

Endothelin1 (EDN1) is well established marker of inflammation. The functions of EDN1 are mediated mainly by endothelin receptors type A (EDNRA). The etiopathogenesis of Hashimoto's thyroiditis (HT) remains still elusive although the role of chronic inflammation and subsequent endothelial dysfunction has been established. This study examined firstly the possible association of EDN1 (G5665Tand T-1370G) and EDNRA (C+70G and G-231A) single nucleotide polymorphisms (SNPs) with the occurrence of HT, and evaluates the relationship between genotypes and clinical/laboratory manifestation of HT.

MATERIALS AND METHODS

We analyzed genotype and allele distributions of above mentioned polymorphisms in 163 patients with HT and 181 healthy controls by real-time PCR combined with melting curve analysis.

RESULTS

No significant associations between HT and variant alleles of EDN1 5665 and -1370, as well as EDNRA +70 and -231 SNPs were found. Haplotype analysis demonstrated that there was a strong (D'=0.76, r(2)=0.487) and weak (D'=0.403, r(2)=0.086) linkage disequilibrium (LD) between EDN1 -1370 and 5665, and between EDNRA -231 and +70 SNPs, respectively. However, haplotype frequencies in patients were similar to those in controls. In addition, it was observed that the EDNRA +70 G allele had protective effect against early (at age before 40 years) disease onset of HT (OR: 0.51, 95% CI=0.32-0.79, p=0.003).

CONCLUSION

Although no significant associations between susceptibility to HT with EDN1 5665 and -1370, as well as with EDNRA+70 and -231 SNPs were found, EDNRA +70 polymorphism was related with decreased risk for early onset HT.

The angiotensin-converting enzyme gene insertion/deletion polymorphism in Indian patients with vitiligo: a case-control study and meta-analysis

BACKGROUND

Vitiligo is a common, acquired, idiopathic depigmenting skin disorder. Although the exact pathogenesis remains unknown, genetic susceptibility and autoimmune responses play a role in vitiligo development. Previous studies have suggested that the D allele of the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene is associated with vitiligo in Indians and Koreans. Furthermore, significantly higher serum ACE levels have been demonstrated in patients with some autoimmune and autoinflammatory disorders.

OBJECTIVES

The objectives were to investigate any association between the ACE I/D polymorphism and vitiligo susceptibility in an Indian population, and to compare serum ACE levels in patients with vitiligo and healthy subjects.

METHODS

The ACE I/D genotypes of 79 patients with vitiligo and 100 normal individuals were determined by polymerase chain reaction amplification. A meta-analysis was done to compare the distribution of the ACE I/D alleles and genotypes in the current and three previous studies. Serum ACE levels were evaluated by enzyme-linked immunosorbent assay.

RESULTS

A significant increase in the frequency of the ACE I/D D allele was evident in patients with vitiligo in both the case-control study [P=0·005; odds ratio (OR) 1·87; 95% confidence intervals (CI) 1·22-2·85] and the meta-analysis (P=0·044; OR 1·44; 95% CI 1·01-2·06). Serum ACE levels were significantly increased in patients with vitiligo compared with healthy subjects (P<0·0001).

CONCLUSIONS

In agreement with earlier reports, the ACE I/D D allele is associated with vitiligo susceptibility in the Indian population. The significantly elevated serum ACE levels in our cohort of patients with vitiligo concur with those previously found in patients with some other autoimmune diseases.

Polymorphisms of endothelin 1 (G5665T and T-1370G) and endothelin receptor type A (C+70G and G-231A) in Graves' disease

PURPOSE

Endothelin 1 (EDN1) is a strong angiogenic and mitogenic factor, playing a key role in hypervascularization, thyroid follicle cell hyperplasia, and lymphocyte infiltration in the thyroid gland of patients with Graves' disease (GD). EDN1 induces angiogenesis and mitogenesis via endothelin receptor type A (EDNRA). This study examined the possible association of EDN1 (G5665T and T-1370G) and EDNRA (C+70G and G-231A) single nucleotide polymorphisms (SNPs) with the occurrence of GD, and evaluates the relationship between genotypes and clinical/laboratory manifestations of GD.

MATERIALS AND METHODS

We analyzed genotype and allele distributions of EDN1 and EDNRA polymorphisms in 165 patients with GD and 181 healthy controls by real-time PCR combined with melting curve analysis.

RESULTS

No significant associations between GD and variant alleles of the studied polymorphisms were observed. However, the anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-TG) levels in EDN1 G5665T GG genotype were higher than those in T allele carriers (GT+TT) (p=0.001 and p=0.026, respectively). In addition, anti-TPO levels in EDN1 T-1370G wild-type homozygous patients were found to be higher than in mutant gene carrying patients (GT+GG) (p=0.006). The presence of EDNRA+70G allele was associated with 3.37-fold increased risk for development of ophthalmopathy in GD patients (p=0.009).

CONCLUSION

Although there were no associations between EDN1 (G5665T and T-1370G) and EDNRA (C+70G and G-231A) SNPs and susceptibility to GD, EDN1 G5665T and T-1370G polymorphisms were related to alterations of autoantibody production and EDNRA C+70G polymorphism is related with increased risk for ophthalmopathy in GD patients.

Polymorphisms of genes related to endothelial cells are associated with primary biliary cirrhosis patients of Cretan origin

BACKGROUND

Primary biliary cirrhosis (PBC) is an organ specific autoimmune disease of still unidentified genetic etiology. We have shown that endothelins (ETs), produced by the liver endothelial cells are increased in PBC and may play a major pathogenetic role.

AIMS

To study gene polymorphisms related to the endothelial cells (eNOS, EDN-1 genes) and, to investigate whether the previously reported association of CTLA4 gene polymorphisms is replicated in a genetically homogeneous Greek population.

PATIENTS AND METHODS

Genomic DNA was extracted from 100 PBC patients (83 females, 93% AMA+, 74/100 Ludwig stage I-II) and 158 healthy controls. eNOS, CTLA4 and ET1 polymorphisms were determined by PCR-RFLPs analysis.

RESULTS

Both eNOS intron4 VNTR and eNOS exon7 G894T SNP were significantly associated with increased risk in PBC. EDN-11 rs2071942 "A" and rs5370 "T" alleles appeared a tendency for association with disease progression. No association was found between PBC and the CTLA4 SNPs analyzed.

CONCLUSIONS

We demonstrated that eNOS, a gene related to the liver endothelium function is associated with PBC. Contrarily, the important in adaptive immunity gene CTLA4 was not associated with the disease in the homogeneous population analyzed. These results are compatible partially with our previous hypothesis that defects of the liver endothelial system, leading to endothelin overproduction, may be a fundamental early pathogenetic mechanism in PBC.

Association of UVRAG polymorphisms with susceptibility to non-segmental vitiligo in a Korean sample

Autoimmune, self-destructive, oxidative stress and genetic theories have been proposed for the pathogenesis of vitiligo. Autophagy is essential for cellular homeostasis and is implicated in many pathophysiological conditions such as cancer, response to oxidative stress and autoimmunity. The ultraviolet (UV) radiation resistance-associated gene (UVRAG) activates the Beclin1-PI(3)KC3 complex, promoting autophagy. To evaluate whether UVRAG polymorphisms are associated with non-segmental vitiligo (NSV) patients in a Korean sample, we conducted a case-control association study of 225 NSV patients and 439 matched healthy controls. A total of five single nucleotide polymorphisms (SNPs) of UVRAG were selected for analysis. Among these, two SNPs (rs1458836, rs7933235) showed significant genotypic differences between the NSV patient group and the control group. These two SNPs were located within a strong linkage disequilibrium (LD) block. In addition, the haplotype of the UVRAG polymorphism was associated with NSV. This study suggests a possible association between UVRAG and NSV susceptibility.

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.

Association of thymic stromal lymphopoietin gene -847C>T polymorphism in generalized vitiligo

Thymic stromal lymphopoietin (TSLP) induces naïve CD4+ T cells to produce Th2 cytokines. In addition, to low production of Th2 cytokines, strong Th1 response, which plays an important role in vitiligo development, has been induced by blockade of TSLP or TSLP receptor. This study examined whether a functional TSLP polymorphism was associated with vitiligo. One hundred and sixty Korean patients with vitiligo and 568 healthy Korean individuals were examined for the four SNPs of TSLP gene. Luciferase activity was measured for promoter assay. The genotype and allele frequencies of -847C>T polymorphism were lower in vitiligo patients compared with the controls, whereas those of wild type were higher (P = 0.004, P = 0.017 respectively). None the less, the promoter activity of -847C decreased significantly (P = 0.013) compared with -847T, expecting lower TSLP mRNA levels in the polymorphism. Collectively, C allele at the TSLP -847C>T polymorphism may increase susceptibility to generalized vitiligo through decreasing TSLP mRNA expression levels.

Candidate EDA targets revealed by expression profiling of primary keratinocytes from Tabby mutant mice

EDA, the gene mutated in anhidrotic ectodermal dysplasia, encodes ectodysplasin, a TNF superfamily member that activates NF-kB mediated transcription. To identify EDA target genes, we have earlier used expression profiling to infer genes differentially expressed at various developmental time points in Tabby (Eda-deficient) compared to wild-type mouse skin. To increase the resolution to find genes whose expression may be restricted to epidermal cells, we have now extended studies to primary keratinocyte cultures established from E19 wild-type and Tabby skin. Using microarrays bearing 44,000 gene probes, we found 385 preliminary candidate genes whose expression was significantly affected by Eda loss. By comparing expression profiles to those from Eda-A1 transgenic skin, we restricted the list to 38 "candidate EDA targets", 14 of which were already known to be expressed in hair follicles or epidermis. We confirmed expression changes for 3 selected genes, Tbx1, Bmp7, and Jag1, both in keratinocytes and in whole skin, by Q-PCR and Western blotting analyses. Thus, by the analysis of keratinocytes, novel candidate pathways downstream of EDA were detected.

A study of a single variant allele (rs1426654) of the pigmentation-related gene SLC24A5 in Greek subjects

The SLC24A5 gene, the human orthologue of the zebrafish golden gene, has been shown to play a key role in human pigmentation. In this study, we investigate the prevalence of the variant allele rs1426654 in a selected sample of Greek subjects. Allele-specific polymerase chain reaction was performed in peripheral blood samples from 158 attendants of a dermatology outpatient service. The results were correlated with pigmentary traits and MC1R genotype. The vast majority of subjects (99%) were homozygous for the Thr(111) allele. Only two subjects from the control group (1.26%) were heterozygous for the alanine and threonine allele. Both of these Thr(111)/Ala(111) heterozygotes carried a single polymorphism of MC1R (one with the V92M variant and another with the V60L variant). Following reports of the rs1426654 polymorphism reaching fixation in the European population, our study of Greek subjects showed a prevalence of the Thr(111) allele, even among subjects with darker skin pigmentation or phototype.