Genetic polymorphism of the Nrf2 promoter region is associated with vitiligo risk in Han Chinese populations

Treatment update for vitiligo based on autoimmune inhibition and melanocyte protection

INTRODUCTION

The treatment of vitiligo remains challenging due to the complexity of its pathogenesis, influenced by genetic factors, oxidative stress and abnormal cell adhesion that collectively impact melanocyte survival and trigger immune system attacks, resulting in melanocyte death. Melanocytes in vitiligo are believed to exhibit genetic susceptibility and defects in cellular mechanisms, such as defects in autophagy, that reduce their ability to resist oxidative stress, leading to increased expression of the pro-inflammatory protein HSP70. The low expression of adhesion molecules, such as DDR1 and E-cadherin, accelerates melanocyte damage and antigen exposure. Consequently, autoimmune attacks centered on IFN-γ-CXCR9/10-CXCR3-CD8⁺ T cells are initiated, causing vitiligo.

AREAS COVERED

This review discusses the latest knowledge on the pathogenesis of vitiligo and potential therapeutic targets from the perspective of suppressing autoimmune attacks and activating melanocytes functions.

EXPERT OPINION

Vitiligo is one of the most challenging dermatological diseases due to its complex pathogenesis with diverse therapeutic targets. Immune suppression, such as corticosteroids and emerging JAK inhibitors, has proven effective in disease progression. However, during the early stages of the disease, it is also important to optimize therapeutic strategies to activate melanocytes for alleviating oxidative stress and improving treatment outcomes.

The Role of Oxidative Stress in Vitiligo: An Update on Its Pathogenesis and Therapeutic Implications

Vitiligo is an autoimmune skin disorder caused by dysfunctional pigment-producing melanocytes which are attacked by immune cells. Oxidative stress is considered to play a crucial role in activating consequent autoimmune responses related to vitiligo. Melanin synthesis by melanocytes is the main intracellular stressor, producing reactive oxygen species (ROS). Under normal physiological conditions, the antioxidative nuclear factor erythroid 2-related factor 2 (Nrf2) pathway functions as a crucial mediator for cells to resist oxidative stress. In pathological situations, such as with antioxidant defects or under inflammation, ROS accumulate and cause cell damage. Herein, we summarize events at the cellular level under excessive ROS in vitiligo and highlight exposure to melanocyte-specific antigens that trigger immune responses. Such responses lead to functional impairment and the death of melanocytes, which sequentially increase melanocyte cytotoxicity through both innate and adaptive immunity. This report provides new perspectives and advances our understanding of interrelationships between oxidative stress and autoimmunity in the pathogenesis of vitiligo. We describe progress with targeted antioxidant therapy, with the aim of providing potential therapeutic approaches.

NRF2, a crucial modulator of skin cells protection against vitiligo, psoriasis, and cancer

The skin represents a physical barrier between the organism and the environment that has evolved to confer protection against biological, chemical, and physical insults. The inner layer, known as dermis, is constituted by connective tissue and different types of immune cells whereas the outer layer, the epidermis, is composed by different layers of keratinocytes and an abundant number of melanocytes, localized in the stratum basale of the epidermis. Oxidative stress is a common alteration of inflammatory skin disorders such as vitiligo, dermatitis, or psoriasis but can also play a causal role in skin carcinogenesis and tumor progression. Nuclear factor (erythroid-derived 2)-like 2 (NRF2) has emerged as a crucial regulator of cell defense mechanisms activating complex transcriptional programs that facilitate reactive oxygen species detoxification, repair oxidative damage and prevent xenobiotic-induced toxicity. Accumulating evidence suggests that the keratinocytes, melanocytes, and other skin cell types express high levels of NRF2, which is known to play a pivotal role in the skin homeostasis, differentiation, and metabolism during normal and pathologic conditions. In the present review, we summarize the current evidence linking NRF2 to skin pathophysiology and we discuss some recent modulators of NRF2 activity that have shown a therapeutic efficacy in skin protection against tumor initiation and common inflammatory skin conditions such as vitiligo or psoriasis, with a particular emphasis on natural compounds.

Heme oxygenase-1 gene rs2071746 polymorphism in retinal vein occlusion

BACKGROUND

Heme oxygenase-1 (HO-1) is an important cytoprotective enzyme due to its ability to degrade pro-inflammatory heme. The common single nucleotide polymorphism (SNP) rs2071746 on the HMOX1 gene has been associated with HO-1 activity and a variety of cardiovascular diseases. This study was performed to investigate the association between the rs2071746 SNP and retinal vein occlusion (RVO).

METHODS

We included 496 RVO patients and 297 control subjects in this case-control study. Genotypes of the rs2071746 polymorphism were determined by TaqMan assays.

RESULTS

There was no association between the rs2071746 genotype and the presence of RVO (p = .443). The lack of association was found in all three logistic regression models, namely the dominant (p = .560), the recessive (p = .373) and the co-dominant model (p = .444). The distribution of the rs2071746 genotype was 30% (AA), 51% (AT), and 19% (TT). Baseline characteristics were similar between these genotypes, except for diabetes mellitus, which was less prevalent in the AA genotype (p < .001).

CONCLUSION

The rs2071746 polymorphism does not seem to be a major risk factor for the presence of RVO.

Inducible Nitric Oxide Synthase iNOS-954-G>C and Ex16+14-C>T Gene Polymorphisms and Susceptibility to Vitiligo in the Saudi Population

Objective

Vitiligo is an acquired pigmentary skin disorder with regional disappearance of melanocytes. Multigenic inheritance has been proposed in the pathogenesis of vitiligo. The present study aimed to investigate the possible association of inducible nitric oxide synthase polymorphisms iNOS-954-G/C (rs1800482 G>C) and iNOS-Ex16+14-C/T (rs2297518 C>T) with vitiligo in the Saudi population, if any.

Methods

We included 120 vitiligo cases and an equal number of age matched healthy controls. Polymerase chain reaction with restriction fragment length polymorphism method was used for the analysis of genetic polymorphisms.

Results

The heterozygous (GC), (GC + CC) combined genotype and variant allele; C allele of rs1800482 G>C were associated significantly (p < 0.005, after Bonferroni correction) with increased risk of vitiligo (OR = 3.46, 95% CI = 1.99–6.01, p = 0.001), (OR = 3.30, 95% CI= 1.93–5.65, p = 0.001) and (OR = 1.94, 95% CI = 1.31–2.87, p = 0.001) respectively. When GC genotype of rs1800482 G>C was co-inherited with common genotype (CC) and heterozygous genotype (CT) of rs2297518 C>T, the risk of vitiligo was significantly increased ((OR = 4.51, 95% CI = 2.18–9.33, p = 0.001) and (OR = 3.60, 95% CI = 1.61–8.01, p = 0.001)) respectively. None of the rs1800482 G>C and rs2297518 C>T genotypes and alleles have been associated with non-segmental vitiligo in terms of gender, age of onset, and types of vitiligo.

Conclusion

The heterozygous (GC), (GC+CC) combined genotype and variants allele; C allele of rs1800482 G>C, may cause overproduction of NO, which has been linked to melanocyte loss by increasing oxidative stress and decreasing melanocyte adhesion to the extracellular matrix components, and thus could be an associative risk factor for vitiligo.

The Role of Oxidative Stress in the Pathogenesis of Vitiligo: A Culprit for Melanocyte Death

Vitiligo is a common chronic acquired pigmentation disorder characterized by loss of pigmentation. Among various hypotheses proposed for the pathogenesis of vitiligo, oxidative stress-induced immune response that ultimately leads to melanocyte death remains most widely accepted. Oxidative stress which causes elevated levels of reactive oxygen species (ROS) can lead to dysfunction of molecules and organelles, triggering further immune response, and ultimately melanocyte death. In recent years, a variety of cell death modes have been studied, including apoptosis, autophagy and autophagic cell death, ferroptosis, and other novel modes of death, which will be discussed in this review in detail. Oxidative stress is also strongly linked to these modes of death. Under oxidative stress, ROS could induce autophagy by activating the Nrf2 antioxidant pathway of melanocytes. However, persistent stimulation of ROS might eventually lead to excessive activation of Nrf2 antioxidant pathway, which in turn will inactivate autophagy. Moreover, ferroptosis may be triggered by oxidative-related transcriptional production, including ARE, the positive feedback loop related to p62, and the reduced activity and expression of GPX4. Therefore, it is reasonable to infer that these modes of death are involved in the oxidative stress response, and that oxidative stress also acts as an initiator for various modes of death through some complex mechanisms. In this study, we aim to summarize the role of oxidative stress in vitiligo and discuss the corresponding mechanisms of interaction between various modes of cell death and oxidative stress. These findings may provide new ideas for exploring the pathogenesis and potential therapeutic targets of vitiligo.

Nuclear Factor Erythroid-2-related Factor 2 Gene Polymorphisms in Vitiligo

BACKGROUND

Oxidative stress is now one of the accepted theories of vitiligo development. Nuclear factor erythroid-2-related factor 2 (Nrf2) regulates the expression of antioxidant proteins.

OBJECTIVE

This work aimed to evaluate the association of Nrf2 gene polymorphisms with the susceptibility to vitiligo among a sample of Egyptian patients with vitiligo.

METHODS

This case-control study included 100 patients with vitiligo and 50 healthy matched volunteers serving as a control group. Genotyping was carried out by real-time polymerase chain reaction.

RESULTS

The frequencies of TT, CT, and combined (TT+CT) genotypes and the T allele of Nrf2 (rs35652124) were significantly increased in the studied patients with vitiligo relative to the healthy controls (p<0.001, p=0.012, p<0.001 and p<0.001, respectively). There was a nonsignificant difference between patients and controls regarding Nrf2 (rs6721961) genotypes. However, the T allele of Nrf2 (rs6721961) was significantly predominant in the studied patients compared to in the controls (p=0.029). Among the studied criteria, the T allele of Nrf2 (rs6721961) was predominant in patients with a marginal type of repigmentation (p=0.022), while the G allele of the same single-nucleotide polymorphism was associated with a higher body mass index value (p=0.034). One hundred percent of patients with vitiligo with the Nrf2 (rs6721961) GT genotype had a progressive disease course (p=0.015).

CONCLUSION

Nrf2 (-617 T/G) and (-653 T/C) polymorphism might play a role in patient susceptibility to vitiligo and modify the clinical presentation of the disease.

Functional Polymorphism in the NFE2L2 Gene Associated With Tuberculosis Susceptibility

Background

Nuclear transcription factor erythroid 2 p45-related factor 2 (Nrf2), encoded by NFE2L2, functions as a key transcription factor and regulates expression of antioxidant genes. Our study aimed to investigate the association of single nucleotide polymorphisms of NFE2L2 with tuberculosis (TB) and latent tuberculosis infection (LTBI) and the underlying causal mechanisms.

Methods

1950 unrelated Chinese Han participants were included in our two independent study groups. Five tag polymorphisms were selected and genotyped. The functional effects of the rs13005431 polymorphism were confirmed by dual-luciferase reporter assays and mRNA level comparisons.

Results

Rs13005431_C and rs2364723_G were associated with increased TB susceptibility (P = 0.010 and P = 0.041) after adjustment for confounding factors. rs6726395_A was associated with increased risk of active TB (P=0.035) in a comparison with the LTBI group. The frequency of haplotype rs1049751- rs13005431 AC was higher in the TB group (P =0.013), while frequency of haplotype AT was higher in the healthy control group (P =0.025). The luciferase activity of a plasmid with the rs13005431C-promoter was significantly lower than that of the rs13005431T-promoter. In addition, neutrophils with the CC/TC genotypes which were activated by GM-CSF showed a decreased level of NFE2L2 mRNA when compared with the rs13005431 TT genotype.

Conclusions

Our study suggests that allele C of rs13005431 might increase the susceptibility to TB by down-regulating the transcriptional activity of NFE2L2.

The role of Nrf2 in autoimmunity and infectious disease: Therapeutic possibilities

Nrf2 is a cytoprotective transcription factor which is involved in ameliorating oxidative stress and toxic insults. Recently, an immunomodulatory role for Nrf2 has gained appreciation as it has been shown to protect cells and hosts alike in a variety of immune and inflammatory disorders. However, Nrf2 utilizes numerous distinct pathways to elicit its immunomodulatory effects. In this review, we summarize the literature discussing the roles of Nrf2 in autoimmunity and infectious diseases with a goal of understanding the potential to therapeutically target Nrf2.

Skin Pigmentation Abnormalities and Their Possible Relationship with Skin Aging

Skin disorders showing abnormal pigmentation are often difficult to manage because of their uncertain etiology or pathogenesis. Abnormal pigmentation is a common symptom accompanying aging skin. The association between skin aging and skin pigmentation abnormalities can be attributed to certain inherited disorders characterized by premature aging and abnormal pigmentation in the skin and some therapeutic modalities effective for both. Several molecular mechanisms, including oxidative stress, mitochondrial DNA mutations, DNA damage, telomere shortening, hormonal changes, and autophagy impairment, have been identified as involved in skin aging. Although each of these skin aging-related mechanisms are interconnected, this review examined the role of each mechanism in skin hyperpigmentation or hypopigmentation to propose the possible association between skin aging and pigmentation abnormalities.

The Association of a Single-Nucleotide Polymorphism in the Nuclear Factor (Erythroid-Derived 2)-Like 2 Gene With Adverse Drug Reactions, Multimorbidity, and Frailty in Older People

Susceptibility to adverse drug reactions (ADRs), multimorbidity, and frailty are associated with human aging, yet there is wide variation in the severity and age at which individuals are afflicted. Identifying genetic markers of increased risk of this phenotype would help stratify individuals to specialist interventions. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) regulates a cell's response to stressors, including the expression of enzymes involved in drug metabolism. Its expression has been shown to decline in animal aging models. In this study, we tested the hypothesis that Nrf2 gene (NFE2L2) transcription/translation decline in human aging and that single-nucleotide polymorphisms (SNPs) in the NFE2L2 gene are associated with increased ADR risk, multimorbidity, and frailty in older people. Gene expression and protein levels were measured in peripheral blood mononuclear cells donated from healthy patients aged 18-80 years old. NFE2L2 genotypes were determined at three loci in a subpopulation of patients recruited to the PRIME study (a multicenter prospective cohort study that followed older adults for 8 weeks post-discharge to determine ADR). Both NFE2L2 gene and Nrf2 protein expression declined significantly with age in human peripheral blood mononuclear cells. In the PRIME substudy population, the rs35652124 NFE2L2 SNP was associated with increased ADR risk and decreased frailty and multimorbidity scores.

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.

Genetic Polymorphism of the Nrf2 Promoter Region (rs35652124) Is Associated with the Risk of Diabetic Foot Ulcers

The genetic polymorphism in the nuclear factor erythroid 2-related factor 2 (Nrf2) gene has been reported as one of the prognosis markers for various diseases, including cancer. Nrf2 is a key transcription factor involved in wound healing by regulating angiogenesis. We investigated the genetic association of NRF2 single-nucleotide polymorphism rs35652124 with T2DM and DFU and assessed its functional impact. A total of 400 subjects were recruited for the study and categorized into three groups: infected DFU patients (DFU, n = 100), T2DM patients without complications (T2DM, n = 150), and healthy adults with normal glucose tolerance (NGT, n = 150). The subjects were genotyped by PCR-RFLP, and the polymorphism was identified by bidirectional Sanger sequencing. The expression of NRF2, IL-10, TNF-α, and IL-6 was studied by qPCR to evaluate the functional impact of rs35652124. The "TT" genotype of rs35652124 was associated with a significant risk for T2DM [OR = 2.2 (1.2-4.2), p = 0.01] and DFU [OR = 7.9 (4-14.9), p < 0.0001]. A significant decrease in transcriptional levels of NRF2 and IL-10 and a remarkable increase in TNF-α and IL-6 were observed in subjects with TT genotype. In conclusion, rs35652124 (TT) is a harmful genetic variant that predisposes to insulin resistance and impaired angiogenesis. Hence, it may serve as a diagnostic genetic marker for T2DM and DFU in combination with different inflammatory markers.

Heme Oxygenases: Cellular Multifunctional and Protective Molecules against UV-Induced Oxidative Stress

Ultraviolet (UV) irradiation can be considered as a double-edged sword: not only is it a crucial environmental factor that can cause skin-related disorders but it can also be used for phototherapy of skin diseases. Inducible heme oxygenase-1 (HO-1) in response to a variety of stimuli, including UV exposure, is vital to maintain cell homeostasis. Heme oxygenase-2 (HO-2), another member of the heme oxygenase family, is constitutively expressed. In this review, we discuss how heme oxygenase (HO), a vital rate-limiting enzyme, participates in heme catabolism and cytoprotection. Phylogenetic analysis showed that there may exist a functional differentiation between HO-1 and HO-2 during evolution. Furthermore, depending on functions in immunomodulation and antioxidation, HO-1 participates in disease progression, especially in pathogenesis of skin diseases, such as vitiligo and psoriasis. To further investigate the particular role of HO-1 in diseases, we summarized the profile of the HO enzyme system and its related signaling pathways, such as Nrf2 and endoplasmic reticulum crucial signaling, both known to regulate HO-1 expression. Furthermore, we report on a C-terminal truncation of HO-1, which is generally considered as a signal molecule. Also, a newly identified alternative splice isoform of HO-1 not only provides us a novel perspective on comprehensive HO-1 alternative splicing but also offers us a basis to clarify the relationship between HO-1 transcripts and oxidative diseases. To conclude, the HO system is not only involved in heme catabolism but also involved in biological processes related to the pathogenesis of certain diseases, even though the mechanism of disease progression still remains sketchy. Further understanding the role of the HO system and its relationship to UV is helpful for revealing the HO-related signaling networks and the pathogenesis of many diseases.

Vitiligo susceptibility at workplace and in daily life: the contribution of oxidative stress gene polymorphisms

Objective

Vitiligo is a frequently underestimated and little known dermal disease whose symptoms appear as white patches on several skin areas of the body. In this review, the impact of idiopathic and chemical-induced vitiligo at workplace and in daily life is discussed. Also, the influence of selected oxidative stress gene polymorphisms on melanocyte damage is described to understand their involvement in the disease.

Methods

A PubMed search was carried out to select the journal articles reporting an association between specific oxidative stress polymorphic genes and vitiligo.

Results

The double-null glutathione S-transferase T1 and M1 genotypes are associated with vitiligo while the relationship between nuclear factor erythroid 2-related factor 2, heme oxygenase, catalase and superoxide dismutase gene polymorphisms and the disease should be confirmed by further studies.

Conclusions

The polymorphic genes analysed here may have a role in the susceptibility of patients affected by vitiligo, while little is known about the affected workers, due to the lack of epidemiologic data on these subjects. However, the similarity of the skin lesions observed in both groups might have in common some genetic factors making all these individuals susceptible to the development of vitiligo, regardless of the disease-triggering factor.

Rare and common genetic variations in the Keap1/Nrf2 antioxidant response pathway impact thyroglobulin gene expression and circulating levels, respectively

Nuclear factor, erythroid 2-like 2 (Nrf2) is a transcription factor that has been gaining attention in the field of pharmacology and especially in the chemoprevention of diseases such as cancer, metabolic and neurodegenerative diseases, etc. This is because natural compounds such as sulforaphane, which is found in broccoli sprout extracts, can activate Nrf2. The repertoire of the roles of Nrf2 is ever increasing; besides its traditional antioxidant and cytoprotective effects, Nrf2 can have other functions as a transcription factor. We have recently shown that Nrf2 directly regulates the expression of thyroglobulin (Tg), which is the most abundant thyroidal protein and the precursor of thyroid hormones. Two functional binding sites for Nrf2 (antioxidant response elements, AREs) were identified in the regulatory region of the TG gene. Interestingly, we then observed that one of these AREs harbors a rare single-nucleotide polymorphism (SNP). Also recently, we performed the first genome-wide association study (GWAS) for common SNPs that impact the circulating levels of Tg. Based on these investigations, we were triggered (i) to investigate whether common SNPs in the Nrf2 pathway correlate with circulating Tg levels; and (ii) to examine whether the rare SNP in one of the TG regulatory AREs may affect gene expression. To address the first question, we analyzed GWAS data from a general population and its two subpopulations, one with thyroid disease and/or abnormal thyroid function tests and the other without, in which circulating Tg levels had been measured. Statistically significant associations with Tg levels were observed in the genes encoding Nrf2 and Keap1, including, notably, a known functional SNP in the promoter of the gene encoding Nrf2. Regarding the rare SNP (rs778940395) in the proximal ARE of the TG enhancer, luciferase reporter gene expression studies in PCCL3 rat thyroid follicular cells showed that this SNP abrogated the basal and sulforaphane- or TSH-induced luciferase activity, behaving as a complete loss-of-function mutation. Thus, both rare and common genetic variation in the Keap1/Nrf2 pathway can impact TG expression and Tg circulating levels, respectively.

Therapeutic targeting of the NRF2 and KEAP1 partnership in chronic diseases

The transcription factor NF-E2 p45-related factor 2 (NRF2; encoded by NFE2L2) and its principal negative regulator, the E3 ligase adaptor Kelch-like ECH-associated protein 1 (KEAP1), are critical in the maintenance of redox, metabolic and protein homeostasis, as well as the regulation of inflammation. Thus, NRF2 activation provides cytoprotection against numerous pathologies including chronic diseases of the lung and liver; autoimmune, neurodegenerative and metabolic disorders; and cancer initiation. One NRF2 activator has received clinical approval and several electrophilic modifiers of the cysteine-based sensor KEAP1 and inhibitors of its interaction with NRF2 are now in clinical development. However, challenges regarding target specificity, pharmacodynamic properties, efficacy and safety remain.

Confronting two biomolecular techniques to detect NRF2 gene polymorphism biomarkers

Aim:

Gene polymorphism biomarkers identify individual susceptibility to environmental and occupational hazards. The conventional approach considers polymerase chain reaction (PCR) followed by restriction fragment length polymorphism analysis (RFLP), a reliable but expensive and time-consuming two-step procedure. Therefore we evaluated the simpler method confronting two-pair primers (CTPP)–PCR for its robustness and applicability to epidemiologic studies.

Materials & methods:

We compared CTPP–PCR and PCR–RFLP techniques to detect two NRF2 polymorphisms in a set of biological samples.

Results:

CTPP–PCR produced contradictory results and required the orthogonal technique for confirming the data.

Conclusion:

In contrast to PCR-RFLP, CTPP–PCR of NRF2 polymorphisms resulted in ambiguous genotyping which strongly jeopardized heterozygosis classification. The necessity of long optimization and control procedures nullified the potential advantages of CTPP–PCR in terms of costs and time.

Confronting two-pair primers-polymerase chain reaction (CTPP–PCR) is potentially a fast, simple and cost-efficient method for the detection of gene polymorphism biomarkers. This technique was used to genotype two SNPs of NRF2 gene in a set of biological samples but resulted in ambiguous results. Therefore, it was necessary to validate the CTPP–PCR genotyping data with the orthogonal technique PCR-RFLP. Since reproducibility is a critical issue in both biomedical research and diagnostics, we advise pairing CTPP–PCR with control methods and evaluating whether the overall package is still convenient for massive genetic screening.

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

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

Identification of the Risk HLA-A Alleles and Autoantigen in Han Chinese Vitiligo Patients and the Association of CD8+T Cell Reactivity with Disease Characteristics

BACKGROUND Multiple studies have implicated a role for CD8+T cell-mediated immune response to autoantigens in vitiligo. However, the antigen-specific T lymphocyte reactivity against the peptide epitopes is diverse among different world populations. This study aimed to identify the risk HLA-A allele in vitiligo and study CD8+ T cell reactivity to 5 autoantigenic peptides in Han Chinese populations, and to analyze the association of CD8+ T cell reactivity with disease characteristics. MATERIAL AND METHODS The risk HLA-A allele was analyzed by case-control study. Enzyme linked immunospot (ELISPOT) assay was used to compare T cell reactivity to the 5 autoantigenic peptides between vitiligo patients and healthy controls, then we analyzed the association of CD8+ T cell reactivity to 2 positive peptides with disease activity and area of skin lesions. RESULTS The results indicated that the most frequent allele in the Han Chinese vitiligo patients was the HLA-A*02: 01 allele with a significantly higher frequency compared to controls (20.20% versus 13.79%, P=6.64×10-5). The most frequently encountered epitopes were 2 gp100 modified peptides, IMDQVPFSV and YLEPGPVTV, whereas a weak T cell reactivity against tyrosinase and Melan-A/MART-1 were evaluated. Moreover, we demonstrated that T cell reactivity against the 2 positive peptides was significantly associated with disease characteristics including disease activity and area of skin lesions. CONCLUSIONS Our findings showed that the HLA-A*02: 01 allele was the major risk HLA-A allele, and 2 gp100 modified peptides were identified as autoantigens and were found to be closely related to disease characteristics which might play a critical role in Han Chinese vitiligo patients.

Vitiligo and Autoimmune Thyroid Disorders

Vitiligo represents the most common cause of acquired skin, hair, and oral depigmentation, affecting 0.5-1% of the population worldwide. It is clinically characterized by the appearance of disfiguring circumscribed skin macules following melanocyte destruction by autoreactive cytotoxic T lymphocytes. Patients affected by vitiligo usually show a poorer quality of life and are more likely to suffer from depressive symptoms, particularly evident in dark-skinned individuals. Although vitiligo is a non-fatal disease, exposure of affected skin to UV light increases the chance of skin irritation and predisposes to skin cancer. In addition, vitiligo has been associated with other rare systemic disorders due to the presence of melanocytes in other body districts, such as in eyes, auditory, nervous, and cardiac tissues, where melanocytes are thought to have roles different from that played in the skin. Several pathogenetic models have been proposed to explain vitiligo onset and progression, but clinical and experimental findings point mainly to the autoimmune hypothesis as the most qualified one. In this context, it is of relevance the strong association of vitiligo with other autoimmune diseases, in particular with autoimmune thyroid disorders, such as Hashimoto thyroiditis and Graves' disease. In this review, after a brief overview of vitiligo and its pathogenesis, we will describe the clinical association between vitiligo and autoimmune thyroid disorders and discuss the possible underlying molecular mechanism(s).

Dysfunction of Autophagy: A Possible Mechanism Involved in the Pathogenesis of Vitiligo by Breaking the Redox Balance of Melanocytes

Vitiligo is a common chronic acquired pigmentation disorder characterized by loss of functional melanocytes from the epidermis and follicular reservoir. Among multiple hypotheses which have been proposed in the pathogenesis of vitiligo, autoimmunity and oxidative stress-mediated toxicity in melanocytes remain most widely accepted. Macroautophagy is a lysosome-dependent degradation pathway which widely exists in eukaryotic cells. Autophagy participates in the oxidative stress response in many cells, which plays a protective role in preventing damage caused by oxidative stress. Recent studies have enrolled autophagy as an important regulator in limiting damage caused by UV light and lipid oxidation, keeping oxidative stress in a steady state in epidermal keratinocytes and maintaining normal proliferation and aging of melanocytes. Impairment of autophagy might disrupt the antioxidant defense system which renders melanocytes to oxidative insults. These findings provide supportive evidence to explore new ideas of the pathogenesis of vitiligo and other pigmentation disorders.

Recent advances in understanding vitiligo

Vitiligo, an acquired depigmentation disorder, manifests as white macules on the skin and can cause significant psychological stress and stigmatization. Recent advances have shed light on key components that drive disease onset and progression as well as therapeutic approaches. Vitiligo can be triggered by stress to the melanin pigment-producing cells of the skin, the melanocytes. The triggers, which range from sunburn to mechanical trauma and chemical exposures, ultimately cause an autoimmune response that targets melanocytes, driving progressive skin depigmentation. The most significant progress in our understanding of disease etiology has been made on three fronts: (1) identifying cellular responses to stress, including antioxidant pathways and the unfolded protein response (UPR), as key players in disease onset, (2) characterizing immune responses that target melanocytes and drive disease progression, and (3) identifying major susceptibility genes. The current model for vitiligo pathogenesis postulates that oxidative stress causes cellular disruptions, including interruption of protein maturation in the endoplasmic reticulum (ER), leading to the activation of the UPR and expression of UPR-regulated chemokines such as interleukin 6 (IL-6) and IL-8. These chemokines recruit immune components to the skin, causing melanocytes to be targeted for destruction. Oxidative stress can further increase melanocyte targeting by promoting antigen presentation. Two key components of the autoimmune response that promote disease progression are the interferon (IFN)-γ/CXCL10 axis and IL-17-mediated responses. Several genome-wide association studies support a role for these pathways, with the antioxidant gene NRF2, UPR gene XBP1, and numerous immune-related genes including class I and class II major histocompatibility genes associated with a risk for developing vitiligo. Novel approaches to promote repigmentation in vitiligo are being investigated and may yield effective, long-lasting therapies.