CXCL10 is critical for the progression and maintenance of depigmentation in a mouse model of vitiligo

The role of regulatory T cells in vitiligo and therapeutic advances: a mini-review

BACKGROUND

Regulatory T cells (Tregs) play vital roles in controlling immune reactions and maintaining immune tolerance in the body. The targeted destruction of epidermal melanocytes by activated CD8+T cells is a key event in the development of vitiligo. However, Tregs may exert immunosuppressive effects on CD8+T cells, which could be beneficial in treating vitiligo.

METHODS

A comprehensive search of PubMed and Web of Science was conducted to gather information on Tregs and vitiligo.

RESULTS

In vitiligo, there is a decrease in Treg numbers and impaired Treg functions, along with potential damage to Treg-related signaling pathways. Increasing Treg numbers and enhancing Treg function could lead to immunosuppressive effects on CD8+T cells. Recent research progress on Tregs in vitiligo has been summarized, highlighting various Treg-related therapies being investigated for clinical use. The current status of Treg-related therapeutic strategies and potential future directions for vitiligo treatment are also discussed.

CONCLUSIONS

A deeper understanding of Tregs will be crucial for advancing Treg-related drug discovery and treatment development in vitiligo.

Greater mechanistic understanding of the cutaneous pathogenesis of Stevens-Johnson syndrome/toxic epidermal necrolysis can shed light on novel therapeutic strategies: a comprehensive review

PURPOSE OF REVIEW

Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) are severe cutaneous adverse drug reactions (SCARs) characterized by widespread epithelial detachment and blistering, which affects the skin and mucocutaneous membranes. To date, therapeutic interventions for SJS/TEN have focused on systematic suppression of the inflammatory response using high-dose corticosteroids or intravenous immunoglobulin G (IgG), for example. No targeted therapies for SJS/TEN currently exist.

RECENT FINDINGS

Though our understanding of the pathogenesis of SJS/TEN has advanced from both an immunological and dermatological perspective, this knowledge is yet to translate into the development of new targeted therapies.

SUMMARY

Greater mechanistic insight into SJS/TEN would potentially unlock new opportunities for identifying or repurposing targeted therapies to limit or even prevent epidermal injury and blistering.

Up-and-Coming Drugs for the Treatment of Vitiligo

Vitiligo is a chronic autoimmune disease that causes depigmented patches on the skin. It affects 0.5%-2.0% of the global population. It goes beyond physical appearance, often leading to stigmatization, low self-esteem, and depression, burdening patients with psychosocial challenges. The pathogenesis of vitiligo involves the loss of melanocytes due to autoreactive CD8+ T cells, triggered by environmental stressors and exacerbated by cellular vulnerabilities and immune responses. The release of danger signals and pro-inflammatory factors initiates an immune cascade perpetuating melanocyte destruction, mainly driven by interferon-γ and the C-X-C motif chemokine ligand 9/10-chemokine receptor 3 axis. Long-lasting tissue-resident memory T cells (Trms) and cytokines contribute to lesion persistence. Current treatments focus on topical steroids and tacrolimus, systemic steroids, and phototherapies, but their efficacy remains suboptimal, necessitating the development of new therapeutic options. Building on recent advancements in understanding the immunological mechanisms in vitiligo pathogenesis, with the initiation of Food and Drug Administration approval of topical ruxolitinib, various potential treatment options such as JAK inhibitors, cytokine blockers, and Trm or regulatory T cell targeting agents are being clinically researched and anticipated for vitiligo based on both preclinical and clinical data. This review aims to categorize and summarize the diverse investigational drugs currently undergoing clinical trials for vitiligo. By examining clinical outcomes, it is anticipated that this review will bring hope to dermatologists and patients regarding vitiligo, a condition that has historically posed challenges and transform it into a realm of potential possibilities.

Association between vitiligo and risk of retinal detachment: a population-based cohort study in Taiwan

BACKGROUND

Vitiligo is reportedly associated with several ocular abnormalities. However, the relationship between vitiligo and retinal detachment (RD) remains unclear.

OBJECTIVES

To examine the risk of RD in patients with vitiligo.

METHODS

A nationwide population-based cohort study was conducted using data from the Taiwan National Health Insurance Database from 2007 to 2018. A total of 21 132 patients with vitiligo were matched in a 1 : 4 ratio with people without vitiligo by age, sex and comorbidity propensity score. Cumulative incidence and Cox proportional hazard models were used to investigate the risk of RD in patients with vitiligo. Subgroup analysis was performed.

RESULTS

The cohort with vitiligo had a significantly higher rate of RD than the cohort without vitiligo [adjusted hazard ratio (aHR) 1.44, 95% confidence interval (CI) 1.20-1.72; P < 0.001]. Patients with vitiligo who required treatments such as phototherapy, systemic corticosteroids or immunosuppressants exhibited an even greater risk of RD (aHR 1.57, 95% CI 1.16-2.14; P = 0.004).

CONCLUSIONS

Our study revealed a 1.44-fold increased risk of RD in patients with vitiligo, with an even higher risk in patients receiving phototherapy, systemic corticosteroids or immunosuppressants. The risk remained consistently higher over a 10-year follow-up period.

Diabetes, glycemic profile and risk of vitiligo: A Mendelian randomization study

BACKGROUD

Previous observational studies have shown that vitiligo usually co-manifests with a variety of dysglycemic diseases, such as Type 1 diabetes mellitus (T1DM) and Type 2 diabetes mellitus (T2DM). Mendelian randomization (MR) analysis was performed to further evaluate the causal association between fasting plasma glucose, glycosylated hemoglobin (HbA1c), T1DM, T2DM and vitiligo.

MATERIALS AND METHODS

We used aggregated genome-wide association data from the Integrative Epidemiology Unit (IEU) online database of European adults vitiligo; HbA1c data were from IEU. Fasting blood glucose data were obtained from the European Bioinformatics Institute (EBI). T1DM and T2DM data were from FinnGen. We used bidirectional two-sample and multivariate MR analyses to test whether dysglycemic measures (fasting blood glucose, HbA1c), diabetes-related measures (T1DM, T2DM) are causatively associated with vitiligo. Inverse variance weighting (IVW) method was used as the main test method, MR-Egger, Weighted mode and Weighted median were used as supplementary methods.

RESULTS

We found no statistically significant evidence to support a causal association between dysglycemic traits and vitiligo, but in the correlation analysis of diabetic traits, our data supported a positive causal association between T1DM and vitiligo (p = 0.018). In the follow-up multivariate MR analysis, our results still supported this conclusion (p = 0.016), and suggested that HbA1c was not a mediator of T1DM affecting the pathogenesis of vitiligo. No reverse causality was found in any of the reverse MR Analyses of dysglycemic traits and diabetic traits.

CONCLUSIONS

Our findings support that T1DM is a risk factor for the development of vitiligo, and this conclusion may explain why the co-presentation of T1DM and vitiligo is often seen in observational studies. Clinical use of measures related to T1DM may be a new idea for the prevention or treatment of vitiligo.

Dysregulated tryptophan metabolism and AhR pathway contributed to CXCL10 upregulation in stable non-segmental vitiligo

BACKGROUND

Tryptophan metabolism dysregulation has been observed in vitiligo. However, drawing a mechanistic linkage between this metabolic disturbance and vitiligo pathogenesis remains challenging.

OBJECTIVE

Aim to reveal the characterization of tryptophan metabolism in vitiligo and investigate the role of tryptophan metabolites in vitiligo pathophysiology.

METHODS

LC-MS/MS, dual-luciferase reporter assay, ELISA, qRT-PCR, small interfering RNA, western blotting, and immunohistochemistry were employed.

RESULTS

Kynurenine pathway activation and KYAT enzyme-associated deviation to kynurenic acid (KYNA) in the plasma of stable non-segmental vitiligo were determined. Using a public microarray dataset, we next validated the activation of kynurenine pathway was related with inflammatory-related genes expression in skin of vitiligo patients. Furthermore, we found that KYNA induced CXCL10 upregulation in keratinocytes via AhR activation. Moreover, the total activity of AhR agonist was increased while the AhR concentration per se was decreased in the plasma of vitiligo patients. Finally, higher KYAT, CXCL10, CYP1A1 and lower AhR expression in vitiligo lesional skin were observed by immunohistochemistry staining.

CONCLUSION

This study depicts the metabolic and genetic characterizations of tryptophan metabolism in vitiligo and proposes that KYNA, a tryptophan-derived AhR ligand, can enhance CXCL10 expression in keratinocytes.

Topical application of simvastatin acid sodium salt and atorvastatin calcium salt in vitiligo patients. Results of the randomized, double-blind EVRAAS pilot study

Contemporary treatment of vitiligo remains a great challenge to practitioners. The vast majority of currently conducted clinical trials of modern therapeutic methods are focused on systemic medications, while there is only a very limited number of reports on new topical treatment in vitiligo. With their pleiotropic activities statins turned out to be efficient in the treatment of various autoimmune/autoinflammatory disorders. The randomized, double-blind placebo-controlled study of topical administration of the active forms of simvastatin and atorvastatin has been designed to evaluate their efficacy in patients with vitiligo. The study was registered in clinicaltrials.gov (registration number NCT03247400, date of registration: 11th August 2017). A total of 24 patients with the active form of non-segmental vitiligo were enrolled in the study. The change of absolute area of skin lesions, body surface area and vitiligo area scoring index were evaluated throughout the 12 week application of ointments containing simvastatin and atorvastatin. Measurements were performed with planimetry and processed using digital software. Use of active forms of simvastatin and atorvastatin did not result in a significant repigmentation of the skin lesions throughout the study period. Within the limbs treated with topical simvastatin, inhibition of disease progression was significantly more frequent than in the case of placebo (p = 0.004), while the difference was not statistically significant for atorvastatin (p = 0.082). Further studies of topical simvastatin in vitiligo patients should be considered.

Parsing patterns: Emerging roles of tissue self-organization in health and disease

Patterned morphologies, such as segments, spirals, stripes, and spots, frequently emerge during embryogenesis through self-organized coordination between cells. Yet, complex patterns also emerge in adults, suggesting that the capacity for spontaneous self-organization is a ubiquitous property of biological tissues. We review current knowledge on the principles and mechanisms of self-organized patterning in embryonic tissues and explore how these principles and mechanisms apply to adult tissues that exhibit features of patterning. We discuss how and why spontaneous pattern generation is integral to homeostasis and healing of tissues, illustrating it with examples from regenerative biology. We examine how aberrant self-organization underlies diverse pathological states, including inflammatory skin disorders and tumors. Lastly, we posit that based on such blueprints, targeted engineering of pattern-driving molecular circuits can be leveraged for synthetic biology and the generation of organoids with intricate patterns.

Cancer Therapy-induced Dermatotoxicity as a Window to Understanding Skin Immunity

Pruritus, rash, and various other forms of dermatotoxicity are the most frequent adverse events among patients with cancer receiving targeted molecular therapy and immunotherapy. Immune checkpoint inhibitors, macrophage-targeting agents, and epidermal growth factor receptor/MEK inhibitors not only exert antitumor effects but also interfere with molecular pathways essential for skin immune homeostasis. Studying cancer therapy-induced dermatotoxicity helps us identify molecular mechanisms governing skin immunity and deepen our understanding of human biology. This review summarizes new mechanistic insights emerging from the analysis of cutaneous adverse events and discusses knowledge gaps that remain to be closed by future research.

Skin Hypopigmentation in Hematology Disorders

Hypopigmentation disorders pose significant diagnostic challenges in dermatology, sometimes reflecting underlying hematological conditions. This review explores the clinical presentations related to hypopigmentation in hematological disorders, focusing on vitiligo, morphea, and syndromic albinism. Vitiligo, an autoimmune disorder targeting melanocytes, involves interactions between genetic polymorphisms and immune responses, particularly regarding CD8+ T cells and IFN-γ. Drug-induced vitiligo, notably by immune checkpoint inhibitors and small-molecule targeted anticancer therapies, underscores the importance of immune dysregulation. Morphea, an inflammatory skin disorder, may signal hematological involvement, as seen in deep morphea and post-radiotherapy lesions. Syndromic albinism, linked to various genetic mutations affecting melanin production, often presents with hematologic abnormalities. Treatment approaches focus on targeting the immune pathways specific to the condition, and when that is not possible, managing symptoms. Understanding these dermatological manifestations is crucial for the timely diagnosis and management of hematological disorders.

Assessment of serum granulysin and cathepsin-L levels in vitiligo patients

OBJECTIVE

Cellular and humoral immunity plays a role in the pathogenesis of vitiligo. T lymphocytes and natural killer cells involved in cellular immunity carry out their cytotoxic activities through perforin/granzyme-dependent granule exocytosis, in which granulysin and cathepsin-L are also involved. The aim of this study was to investigate the possible role of serum granulysin and cathepsin-L in the etiopathogenesis of vitiligo and their association with disease activity and severity.

METHODS

This randomized, prospective case-control study was conducted with 46 vitiligo patients admitted to the hospital for vitiligo between January and November 2021 and 46 healthy volunteers of similar age and gender. Serum levels of granulysin and cathepsin-L were measured by the enzyme-linked immunosorbent assay method.

RESULTS

The mean serum levels of granulysin and cathepsin-L were statistically significantly higher in vitiligo patients compared with the control group (p=0.048 and p=0.024, respectively). There was no statistically significant correlation between serum granulysin and serum cathepsin-L levels and disease severity in the patient group (r=0.30, p=0.062 and r=0.268, p=0.071, respectively). Disease activity also showed no significant association with serum granulysin and cathepsin-L levels (p=0.986 and p=0.962, respectively).

CONCLUSION

Although granulysin and cathepsin-L are molecules involved in the pathogenesis of vitiligo, the use of these molecules may not be helpful in assessing disease activity and severity. It may be helpful to conduct comprehensive and prospective studies to find new molecules to fill the gap in this area.

Vitiligo: advances in pathophysiology research and treatment development

The autoimmune condition vitiligo, characterized by skin depigmentation, presents challenges for effective treatment design, with Janus kinase (JAK) inhibitors and other repurposed drugs offering a promising strategy for symptom management. This review explores advantages and shortcomings of current therapies, while presenting the urgent need for further innovative approaches. We emphasize the growing understanding of autoimmune involvement in vitiligo, highlighting several novel treatment avenues including relieving melanocyte stress, preventing dendritic cell activation, halting T cell migration, and suppressing inflammation and autoimmunity. Integrating psychodrama therapy to remediate stress alongside medical interventions marks a holistic approach to enhance patient well-being. The molecular underpinnings of vitiligo care are covered, emphasizing exciting advances revolutionizing vitiligo treatment and improving the quality of life for affected individuals.

A Mendelian randomization study on the causal effects of circulating cytokines on the risk of vitiligo

Background

Accumulating evidence reveals an association between circulating cytokine levels and vitiligo. However, the causal association between circulating cytokine levels and vitiligo remains unrevealed.

Methods

We performed a two-sample Mendelian randomization (MR) analysis using a genome-wide association study of the 41 cytokines dataset, which was conducted with 3 Finnish cohorts (n = 8,293). Vitiligo data were acquired from strictly defined vitiligo data collected by FinnGenbiobank analysis, which included 207,613 European ancestors (131 vitiligo patients, 207,482 controls). The inverse-variance weighted (IVW) method, weighted median (WME), simple model, weighted model, and MR-Egger were used to determine the changes in vitiligo pathogenic cytokine taxa, followed by sensitivity analysis, including horizontal pleiotropy analysis. The MR Steiger test evaluated the strength of a causal association, and the leave-one-out method was used to assess the reliability of the results. The possibility of reverse causality was also investigated using a reverse MR study.

Results

We observed that rising IL-4 levels generated an enhanced probability of vitiligo in IVW (OR 2.72, 95%CI 1.19-6.22, p = 0.018). According to the results of the MR analysis, there were causal links between IL-4 and vitiligo. Results were steady after sensitivity and heterogeneity analyses.

Conclusion

Our research reveals that a genetically determined increased level of circulating IL-4 may be linked to a higher risk of developing vitiligo. The development of innovative treatment approaches (such as tofacitinib or dupilumab) that focus on blocking IL-4 as a novel way of preventing and treating vitiligo is significantly impacted by our findings.

Pathogenesis of Alopecia Areata and Vitiligo: Commonalities and Differences

Both alopecia areata (AA) and vitiligo are distinct, heterogenous, and complex disease entities, characterized by nonscarring scalp terminal hair loss and skin pigment loss, respectively. In AA, inflammatory cell infiltrates are in the deep reticular dermis close to the hair bulb (swarm of bees), whereas in vitiligo the inflammatory infiltrates are in the epidermis and papillary dermis. Immune privilege collapse has been extensively investigated in AA pathogenesis, including the suppression of immunomodulatory factors (e.g., transforming growth factor-β (TGF-β), programmed death-ligand 1 (PDL1), interleukin-10 (IL-10), α-melanocyte-stimulating hormone (α-MSH), and macrophage migration inhibitory factor (MIF)) and enhanced expression of the major histocompatibility complex (MHC) throughout hair follicles. However, immune privilege collapse in vitiligo remains less explored. Both AA and vitiligo are autoimmune diseases that share commonalities in pathogenesis, including the involvement of plasmacytoid dendritic cells (and interferon-α (IFN- α) signaling pathways) and cytotoxic CD8+ T lymphocytes (and activated IFN-γ signaling pathways). Blood chemokine C-X-C motif ligand 9 (CXCL9) and CXCL10 are elevated in both diseases. Common factors that contribute to AA and vitiligo include oxidative stress, autophagy, type 2 cytokines, and the Wnt/β-catenin pathway (e.g., dickkopf 1 (DKK1)). Here, we summarize the commonalities and differences between AA and vitiligo, focusing on their pathogenesis.

The IFN-γ-CXCL9/CXCL10-CXCR3 axis in vitiligo: Pathological mechanism and treatment

Vitiligo is a disease featuring distinct white patches that result from melanocyte destruction. The overall pathogenesis of vitiligo remains to be elucidated. Nevertheless, considerable research indicates that adaptive immune activation plays a key role in this process. Specifically, the interferon-gamma (IFN-γ), C-X-C motif chemokine ligands (CXCL9/10), and C-X-C motif chemokine receptor (CXCR3) signaling axis, collectively referred to as IFN-γ-CXCL9/10-CXCR3 or ICC axis, has emerged as a key mediator responsible for the recruitment of autoimmune CXCR3+ CD8+ T cells. These cells serve as executioners of melanocytes by promoting their detachment and apoptosis. Moreover, IFN-γ is generated by activated T cells to create a positive feedback loop, exacerbating the autoimmune response. This review not only delves into the mechanistic insights of the ICC axis but also explores the significant immunological effects of associated cytokines and their receptors. Additionally, the review provides a thorough comparison of existing and emerging treatment options that target the ICC axis for managing vitiligo. This review aims to foster further advancements in basic research within related fields and facilitate a deeper understanding of alternative treatment strategies targeting different elements of the axis.

Serum cytokine profiles predict response to systemic glucocorticoid in active vitiligo

Introduction

Vitiligo is an immune-related skin disease. Cytokines regulate immune response and inflammation and are involved in the pathogenesis of vitiligo.

Aim

To assess the serum levels of pro-inflammatory cytokines pre- and post- systemic glucocorticoid treatment in patients with active vitiligo.

Material and methods

We measured serum cytokine levels using the enzyme-linked immunosorbent assay in 31 patients with active vitiligo before and after treatment. All patients received systemic glucocorticoid (compound betamethasone injection) in combination with topical halometasone cream and tacrolimus ointment for 3 months. Twenty healthy controls were also examined. The cytokines measured included TNF-α, IL-1β, IL-6, IFN-γ, IL-2, IL-17, IL-10, IL-8, and CXCL10.

Results

The serum levels of TNF-α, IL-1β, IL-6, IFN-γ, IL-2, IL-17, IL-8, and CXCL10 were significantly higher, and levels of IL-10 were lower in vitiligo patients compared to controls. Additionally, serum IFN-γ (r = 0.378; p = 0.036), IL-17 (r = 0.426; p = 0.017), and CXCL10 (r = 0.514; p = 0.003) showed a positive correlation with affected body surface area in vitiligo patients. After 3 months of systemic glucocorticoid treatment, the levels of IL-1β, IFN-γ, IL-2, IL-17, and CXCL10 in responders were significantly decreased and nearly restored to normal levels. The IL-10 level was also increased in response to treatment. In contrast, the non-responder group had persistently high IL-6, IL-17, IL-8, and CXCL10 levels, and negligible changes in TNF-α, IL-1β, IFN-γ, IL-2, and IL-10.

Conclusions

Our study indicated that the levels of inflammatory cytokines were significantly ameliorated in the glucocorticoid responder group. Altered cell-mediated immunity may contribute to the resistance in vitiligo. The cytokines such as TNF-α, IL-1β, IFN-γ and IL-2 could serve as therapeutic targets for managing glucocorticoid-resistant vitiligo.

Animal models unraveling the complexity of vitiligo pathogenesis

Vitiligo is a chronic skin condition marked by the gradual loss of pigmentation, leading to the emergence of white or depigmented patches on the skin. The exact cause of vitiligo remains not entirely understood, although it is thought to involve a blend of genetic, autoimmune, and environmental factors. While there is currently no definitive cure for vitiligo, diverse treatments exist that may assist in managing the condition and fostering repigmentation in specific instances. Animal models play a pivotal role in comprehending the intricate mechanisms that underlie vitiligo, providing valuable insights into the progression and onset of the disease, as well as potential therapeutic interventions. Although induced experimental models lack the nuanced characteristics observed in natural experimental models, relying solely on a single animal model might not fully capture the intricate pathogenesis of vitiligo. Different animal models simulate specific aspects of human vitiligo pathogenesis to varying degrees. This review extensively explores the array of animal models utilized in vitiligo research, shedding light on their respective advantages, disadvantages, and applications.

Clinical profile of vitiligo patients and relationship with immuno-inflammatory markers

BACKGROUND

Vitiligo is the most common pigmentary disorder and is considered a chronic, cumulative, multifactorial disease. The crucial role of cytotoxic CD8+ T lymphocytes and the IFNγ/CXCL10 axis has been demonstrated in its pathogenesis.

OBJECTIVE

To evaluate the clinical profile and immuno-inflammatory markers in patients with vitiligo in a reference medical center.

METHODS

Cross-sectional study in which all patients with vitiligo seen at the medical center the from 2019 to 2022 were evaluated, to outline the clinical profile. Moreover, cardiovascular risk biomarkers (neutrophil/lymphocyte ratio and C-reactive protein levels) were measured, as well as cytokines and chemokines (TNFα, IFNγ, IL10, IL15 and CXCL10) in the serum of a subgroup of 30 patients.

RESULTS

There was a predominance of females, with a mean age of 43 years. Most were phototypes IV or V (71.3%), without comorbidities (77.55%), and without a family history of vitiligo (70.41%). Higher levels of neutrophil/lymphocyte ratio, C-reactive protein, and inflammatory cytokines/chemokines were documented in vitiligo patients when compared to the control group (non-significant). As relevant data, the highest values of CXCL10 were detected in patients with vitiligo versus controls, as well as in patients with disease of shorter duration (p<0.05).

STUDY LIMITATIONS

The number of assessed patients was small due to recruitment difficulties caused by the COVID-19 pandemic.

CONCLUSION

The present data contribute to confirming the relevant role of the IFNγ/CXCL10 axis in the pathogenesis of vitiligo, highlighting CXCL10 as a possible activity marker.

Bridging Molecular Mechanism and Clinical Practice in Vitiligo Treatment: An Updated Review

BACKGROUND

Treatment of vitiligo seeks to achieve three goals: cessation of disease progression, regeneration of pigmentation, and prevention of recurrence.

SUMMARY

Number of nonsurgical interventions are available that suppress the autoimmune response and regenerate the melanocytes from the reservoir: phototherapy including psoralen and ultraviolet A, narrowband ultraviolet B, and 308-nm excimer and 311-nm Titanium:Sapphire lasers; topical agents including topical calcineurin inhibitors, topical corticosteroids, and topical 5-fluorouracil; and systemic agents including corticosteorids, mycophenolate mofetil, cyclosporine, methotrexate, minocycline, afamelanotide, and antioxidants. In recent years, a great advance has been made in the understanding of pathogenesis of vitiligo, and JAK inhibitors are being investigated as a new treatment. Minimally invasive procedures such as fractional lasers or microneedling can help achieve the optimal treatment outcome when used properly.

KEY MESSAGES

Our review describes various treatment modalities for vitiligo based on their molecular mechanism of action. Bridging the gap between molecular mechanisms and therapeutic options would be a valuable reference for physicians in clinical practice.

Identification of Shared Biomarkers and Immune Infiltration Signatures between Vitiligo and Hashimoto's Thyroiditis

Background

Vitiligo and Hashimoto's thyroiditis (HT) are concomitant autoimmune diseases characterized by the destruction of melanocytes or thyrocytes. We aimed to explore the immunological mechanism of this comorbidity and screen their potential biomarkers.

Methods

We downloaded the microarray datasets from the GEO database. Differentially expressed genes (DEGs) and immune-related genes (IRGs) were selected. The immune-related differentially expressed genes (IRDEGs) were obtained by taking the intersection. Candidate biomarkers were elected by Cytoscape software. CIBERSORT was used to depict immune cell infiltration prospects. Correlation analysis was conducted between infiltrating cells and several indicators. The results were validated by real-time quantitative PCR (RT-qPCR).

Results

Three datasets and 60 IRDEGs were obtained in total. Pathway enrichment analysis showed that the T cell receptor signaling pathway, IL-17 signaling pathway, receptor-ligand activity, and signaling receptor activator activity were significantly enriched. We screened out four hub genes, including IFNG, STAT1, IL1B, and CXCL10. The ROC curve indicated the highest diagnostic value of CXCL10 in both vitiligo and HT. Immuno-infiltration analysis revealed significant changes in T cell subsets and macrophage subtypes, which were correlated with four hub genes, melanocyte markers, and thyroid-specific antigens. qPCR validated the hub genes in peripheral blood mononuclear cells from patients with comorbidity.

Conclusion

IFNG, STAT1, IL1B, and CXCL10, were the key IRDEGs to vitiligo and HT. These genes may participate in the comorbidity by remodeling the immune cell infiltration pattern, and cross-expressed antigens may mediate the common damage of melanocytes and thyroid tissues.

Janus-kinase inhibitors in dermatology: A review of their use in psoriasis, vitiligo, systemic lupus erythematosus, hidradenitis suppurativa, dermatomyositis, lichen planus, lichen planopilaris, sarcoidosis and graft-versus-host disease

Recent studies on molecular pathways have elucidated novel therapeutic approaches in inflammatory and autoimmune skin disorders. Specifically, the dysregulation of the Janus kinase signal transducer and activator of transcription (JAK-STAT) cascade plays a central role in the pathogenesis of many skin conditions. JAK inhibitors, with their ability to selectively target immune responses, are potential treatment options. Using the National Library of Medicine, we provide a comprehensive review of the use of United States Food and Drug Administration (FDA)-approved and emerging JAK or tyrosine kinase 2 (TYK2) inhibitors in a wide range of dermatologic conditions, including psoriasis, vitiligo, systemic lupus erythematosus, hidradenitis suppurativa, dermatomyositis, lichen planus, lichen planopilaris, sarcoidosis and graft-versus-host disease. In patients with psoriasis, oral deucravacitinib (TYK2 inhibitor) has been approved as a once-daily therapy with demonstrated superiority and efficacy over apremilast and placebo and tolerable safety profiles. In patients with vitiligo, topical ruxolitinib (JAK1 inhibitor) is approved as a twice-daily treatment for repigmentation. The efficacy of several other JAK inhibitors has also been demonstrated in several clinical trials and case studies for systemic lupus erythematosus, hidradenitis suppurativa, dermatomyositis, lichen planus, lichen planopilaris, sarcoidosis and graft-versus-host disease. Further investigations with long-term clinical trials are necessary to confirm their utility in treatment and safety for these diseases.

The Involvement of Cysteine-X-Cysteine Motif Chemokine Receptors in Skin Homeostasis and the Pathogenesis of Allergic Contact Dermatitis and Psoriasis

Members of the C-X-C motif chemokine receptor (CXCR) superfamily play central roles in initiating the innate immune response in mammalian cells by orchestrating selective cell migration and immune cell activation. With its multilayered structure, the skin, which is the largest organ in the body, performs a crucial defense function, protecting the human body from harmful environmental threats and pathogens. CXCRs contribute to primary immunological defense; these receptors are differentially expressed by different types of skin cells and act as key players in initiating downstream innate immune responses. While the initiation of inflammatory responses by CXCRs is essential for pathogen elimination and tissue healing, overactivation of these receptors can enhance T-cell-mediated autoimmune responses, resulting in excessive inflammation and the development of several skin disorders, including psoriasis, atopic dermatitis, allergic contact dermatitis, vitiligo, autoimmune diseases, and skin cancers. In summary, CXCRs serve as critical links that connect innate immunity and adaptive immunity. In this article, we present the current knowledge about the functions of CXCRs in the homeostasis function of the skin and their contributions to the pathogenesis of allergic contact dermatitis and psoriasis. Furthermore, we will examine the research progress and efficacy of therapeutic approaches that target CXCRs.

Compromised melanocyte survival due to decreased suppression of CD4+ & CD8+ resident memory T cells by impaired TRM-regulatory T cells in generalized vitiligo patients

Regulatory T cells (Tregs) are involved in the suppression of activated T cells in generalized vitiligo (GV). The study was aimed to investigate resident memory (TRM)-Tregs and antigen-specific Tregs' numbers and functional defects in 25 GV patients and 20 controls. CD4+ & CD8+ TRM cell proliferation was assessed by BrDU assay; production of IL-10, TGF-β, IFN-γ, perforin and granzyme B were assessed by ELISA and enumeration of TRM cells was done by flowcytometry. GV patients showed significantly increased frequency and absolute count of CD4+ & CD8+ TRM cells in lesional (L), perilesional (PL) and non-lesional (NL) skin compared to controls (p = 0.0003, p = 0.0029 & p = 0.0115, respectively & p = 0.0003, p = 0.003 & p = 0.086, respectively). Whereas, TRM-Treg (p < 0.0001 & p = 0.0015) and antigen-specific Tregs (p = 0.0014 & p = 0.003) exhibited significantly decreased frequency and absolute counts in L & PL skin. GV patients showed reduced suppression of CD8+ & CD4+ TRM cells (with increased IFN-γ, perforin & granzyme B) and decreased TRM-Tregs and antigen-specific Tregs (with decreased IL-10 & TGF-β production) and reduced proliferation of SK-Mel-28 cells in co-culture systems. Immunohistochemistry revealed increased expression of TRM stimulating cytokines: IL-15 & IL-17A and reduced expression of TGF-β & IL-10 in L, PL, NL skins compared to controls. These results for the first time suggest that decreased and impaired TRM-Tregs and antigen-specific Tregs are unable to suppress CD4+ & CD8+ TRMs' cytotoxic function and their proliferation due to decrease production of immunosuppressive cytokines (IL-10 & TGF-β) and increased production of TRM based IFN-γ, perforin and granzyme B production, thus compromising the melanocyte survival in GV.

Aetiopathogenesis of Vitiligo

Vitiligo is a chronic auto-immune disease characterized by skin depigmentation due to the loss of melanocytes. The better understanding of the disease mechanisms is currently undergoing a significant dynamism, opening a new era in therapeutic development. The pathophysiology of vitiligo has attracted the attention of researchers for years and many advances have been made in clarifying the crosstalk between the cellular players involved in the development of vitiligo lesions. The understanding of the complex interactions between epidermal cells (i.e. melanocytes and keratinocytes), dermal fibroblasts, and immune cells, led to a better characterization of the signals leading to the loss of melanocytes. Recent advances highlighted the role resident T memory cells in the development and recurrence of lesions. This narrative review aims to give an overview of the mechanisms leading to melanocyte disappearance in vitiligo, with a focus on the intercellular interaction network involved in the activation of the local skin immune response.

Rational design of a JAK1-selective siRNA inhibitor for the modulation of autoimmunity in the skin

Inhibition of Janus kinase (JAK) family enzymes is a popular strategy for treating inflammatory and autoimmune skin diseases. In the clinic, small molecule JAK inhibitors show distinct efficacy and safety profiles, likely reflecting variable selectivity for JAK subtypes. Absolute JAK subtype selectivity has not yet been achieved. Here, we rationally design small interfering RNAs (siRNAs) that offer sequence-specific gene silencing of JAK1, narrowing the spectrum of action on JAK-dependent cytokine signaling to maintain efficacy and improve safety. Our fully chemically modified siRNA supports efficient silencing of JAK1 expression in human skin explant and modulation of JAK1-dependent inflammatory signaling. A single injection into mouse skin enables five weeks of duration of effect. In a mouse model of vitiligo, local administration of the JAK1 siRNA significantly reduces skin infiltration of autoreactive CD8+ T cells and prevents epidermal depigmentation. This work establishes a path toward siRNA treatments as a new class of therapeutic modality for inflammatory and autoimmune skin diseases.

Baseline Levels of Circulating Inflammatory Biomarkers Stratify Patients with Vitiligo Who Significantly Repigment after Treatment with Ruxolitinib Cream

BACKGROUND

Efficacy of ruxolitinib cream, a topical Jak1/Jak2 inhibitor, was demonstrated in a phase 2 trial in patients with vitiligo.

OBJECTIVE

This study aimed to characterize circulating inflammatory biomarker profiles in patients who demonstrated ≥50% improvement in facial Vitiligo Area Scoring Index scores by week 24 (group 1) and those who did not (group 2).

DESIGN

This was a posthoc analysis of a multicenter, randomized, double-blind, vehicle-controlled, phase 2 study in which screening was conducted between June 7, 2017 and March 21, 2018.

POPULATION

Patients aged between 18 and 75 years with vitiligo, including depigmentation affecting ≥0.5% of body surface area on the face and ≥3% of body surface area on nonfacial areas, were eligible.

INTERVENTION

Patients applied 1.5% ruxolitinib cream to lesions once or twice daily for 52 weeks.

MAIN OUTCOMES AND MEASURES

Patients were grouped by achievement of ≥50% improvement in facial Vitiligo Area Scoring Index at week 24. Proteomic analysis was performed on baseline serum samples.

RESULTS

Mean ± standard error facial Vitiligo Area Scoring Index in group 1 (n = 30) versus group 2 (n = 27) improved by 79.9 ± 4.0% versus 1.1 ± 7.3% and 91.9 ± 1.5% versus 25.1 ± 13.4% at weeks 24 and 52, respectively. Broad proteomic analysis revealed 76 proteins (of 1,104 tested) that were differentially expressed between groups 1 and 2 at baseline (P < 0.05). Ten distinct proteins were upregulated in group 1; 64 were elevated in group 2.

CONCLUSION

This analysis identified potential differences between patients who achieved ≥50% improvement in facial Vitiligo Area Scoring Index at 24 weeks and those who did not that require deeper scientific interrogation and may be important in stratifying therapeutic benefit for patients with vitiligo.

TRIAL REGISTRATION

The original study was registered at ClinicalTrials.gov, NCT03099304.

Topical ruxolitinib: A new treatment for vitiligo

Vitiligo is a chronic autoimmune skin disorder whose diagnosis is often psychologically upsetting. The efficacy of the available therapies, including topical corticosteroids and topical calcineurin inhibitors, has historically been limited and the management of vitiligo is still challenging. As vitiligo is a chronic disease limited to the skin, topical rather than systemic therapies may be preferable (especially among patients with localised lesions) to avoid the long-term side-effects of the latter. A topical formulation of ruxolitinib, a selective JAK1/2 inhibitor, has recently been approved in the United States for the treatment of non-segmental vitiligo in patients aged >12 years based on data from the phase III TRuE-V1 and TRuE-V2 clinical trials. The aim of this review is to describe the current evidence concerning the efficacy and safety of topical ruxolitinib in the treatment of vitiligo, and discuss issues regarding its use in younger children and pregnant or breastfeeding women, as well as the duration and durability of treatment. The promising results obtained so far suggest that 1.5% ruxolitinib cream is an effective means of treating vitiligo.

Lesional CD8+ T-Cell Number Predicts Surgical Outcomes of Melanocyte-Keratinocyte Transplantation Surgery for Vitiligo

The melanocyte-keratinocyte transplantation procedure (MKTP) treats stable and recalcitrant vitiligo. Despite careful selection of candidates based on clinical stability, the success of the procedure is unpredictable. The aim of our study was to define the immunological profile of stable vitiligo lesions undergoing MKTP and correlate them with clinical outcomes. We included 20 MKTP candidates with vitiligo and a patient with piebaldism as a control. Prior to MKTP, T-cell subsets and chemokines in the recipient skin were measured by flow cytometry and ELISA. During MKTP, melanocytes in the donor skin were quantified by flow cytometry. After MKTP, patients were followed for 12 months and repigmentation was assessed clinically and by ImageJ analysis of clinical photographs. Baseline immunologic biomarkers, duration of clinical stability, and transplanted melanocyte number were correlated to postsurgical repigmentation scores. CD8+ T cells were elevated in 43% of the clinically stable vitiligo lesions. CD8+ T-cell number negatively correlated with postsurgical repigmentation scores (r = -0.635, P = 0.002). Duration of clinical stability, skin chemokines, and transplanted melanocyte number did not influence postsurgical repigmentation. This study demonstrates that CD8+ T-cell number correlates negatively with success of postsurgical repigmentation and can be a biomarker to identify ideal surgical candidates.

Immune dysregulation and inflammation causing hypopigmentation in post kala-azar dermal leishmaniasis: partners in crime?

Post kala-azar dermal leishmaniasis (PKDL), a heterogeneous dermal sequela of visceral leishmaniasis (VL), is challenging in terms of its etiopathogenesis. Hypopigmentation is a consistent clinical feature in PKDL, but mechanisms contributing to the loss of melanocytes remains poorly defined. Like other hypopigmentary dermatoses - for example, vitiligo, psoriasis, and leprosy - the destruction of melanocytes is likely a multifactorial phenomenon, key players being immune dysregulation and inflammation. This review focuses on immunological mechanisms responsible for the 'murder' of melanocytes, prime suspects at the lesional sites being CD8+ T cells and keratinocytes and their criminal tools being proinflammatory cytokines, for example, IFN-γ, IL-6, and TNF-α. Collectively, these may cause decreased secretion of melanocyte growth factors, loss/attenuation of cell adhesion molecules and inflammasome activation, culminating in melanocyte death.

Gene Expression Signatures in Inflammatory and Sclerotic Morphea Skin and Sera Distinguish Morphea from Systemic Sclerosis

Morphea is an inflammatory fibrotic disorder of the skin that has been likened to systemic sclerosis (SSc). We sought to examine the molecular landscape of morphea by examining lesional skin gene expression and blood biomarkers and comparing the gene expression profiles with those from site-matched nonlesional and SSc lesional skin. We found the morphea transcriptome is dominated by IFN-γ-mediated T helper 1 immune dysregulation, with a relative paucity of fibrosis pathways. Specifically, expression profiles of morphea skin clustered with the SSc inflammatory subset and were distinct from the those of SSc fibroproliferative subset. Unaffected morphea skin also differed from unaffected SSc skin because it did not exhibit pathological gene expression signatures. Examination of downstream IFN-γ-mediated chemokines, CXCL9 and CXCL10, revealed increased transcription in the skin but not in circulation. In contrast to transcriptional activity, CXCL9 was elevated in serum and was associated with active, widespread cutaneous involvement. Taken together, these results indicate that morphea is a skin-directed process characterized by T helper 1 immune-mediated dysregulation, which contrasts with fibrotic signatures and systemic transcriptional changes associated with SSc. The similarity between morphea and the inflammatory subset of SSc on transcriptional profiling indicates that therapies under development for this subset of SSc are also promising for treatment of morphea.

Serum Inflammatory and Oxidative Stress Markers in Patients with Vitiligo

BACKGROUND

Vitiligo is a common chronic hypomelanotic skin disorder. An intricate pool of markers associated with a complex combination of biological and environmental factors is thought to be implicated in etiology. This study aims to investigate the most important markers associated with vitiligo pathogenesis, including redox status, inflammation, and immune profile, in patients with vitiligo.

MATERIALS AND METHODS

The study included a total of 96 subjects: 30 patients with active non-segmental vitiligo, 30 patients with stable non-segmental vitiligo, and 36 controls. The vitiligo area severity index (VASI) and vitiligo disease activity score (VIDA) were determined. The following serum parameters were assessed: antioxidant status (TAS), superoxide dismutase activity (SOD), catalase activity (CAT), glutathione peroxidase activity (GPx), glutathione-S-transferase activity (GST), malondialdehyde (MDA), advanced oxidation protein products (AOPP), C reactive protein (CRP), interleukin-15 (IL-15), and chemokines (CXCL9, CXCL10).

RESULTS

The VASI score was not significantly different between active and stable vitiligo patients, as it was approximately 0.1. TAS, CAT, GPx, and GST were significantly lower in vitiligo patients compared to controls (p < 0.05). They were also significantly lower in active vitiligo when compared to stable vitiligo (p < 0.05). However, SOD levels were significantly higher in vitiligo patients than in controls and in the active vitiligo group than in the stable vitiligo group (p < 0.05). MDA and AOPP levels were significantly higher in patients with active and stable vitiligo compared to controls (p < 0.05). However, they did not significantly differ between active and stable vitiligo patients (p < 0.05). In both active and stable vitiligo, CRP and IL-15 were significantly higher than controls (p < 0.05). Whereas CRP was significantly higher in active (range = 2.0-7.2, mean = 4.46 ± 1.09) than in stable vitiligo (range = 1.6-6.7, mean = 3.75 ± 1.08) (p < 0.05). There was no significant difference in IL-15 levels between active and stable vitiligo. In both active and stable vitiligo, CXCL9 and CXCL10 were significantly higher than controls (p < 0.05), and they were significantly higher in active than stable vitiligo (p < 0.05).

CONCLUSIONS

In vitiligo, oxidative damage induces an increase in pro-inflammatory IL-15, which in turn promotes IFN-γ-inducible chemokines such as CXCL9 and CXCL10. Further, there seems to be a link between the VASI score and IL-15 levels. These data imply that inhibiting IL-15 could be a promising method for developing a potentially targeted treatment that suppresses the early interplay between oxidant stress and IL-15 keratinocyte production, as well as between resident and recirculating memory T cells.

Generalized Vitiligo After Stem Cell Transplantation: A Case Report

Graft versus host disease (GVHD) is a complex immune-mediated pathophysiological process, which is caused by allogenic immune reactions between donors and recipients. No matter ac-ute or chronic GVHD, skin involvement is the most common, severe skin damage can lead to permanent disfigurement, which seriously affects the long-term quality of life of patients. We herein report a patient with generalized vitiligo after allogeneic peripheral hematopoietic stem cell transplantation (allo-HSCT) for aplastic anemia.

Pharmacological inhibition of demethylzeylasteral on JAK-STAT signaling ameliorates vitiligo

BACKGROUND

The activation of CD8⁺ T cells and their trafficking to the skin through JAK-STAT signaling play a central role in the development of vitiligo. Thus, targeting this key disease pathway with innovative drugs is an effective strategy for treating vitiligo. Natural products isolated from medicinal herbs are a useful source of novel therapeutics. Demethylzeylasteral (T-96), extracted from Tripterygium wilfordii Hook F, possesses immunosuppressive and anti-inflammatory properties.

METHODS

The efficacy of T-96 was tested in our mouse model of vitiligo, and the numbers of CD8⁺ T cells infiltration and melanocytes remaining in the epidermis were quantified using whole-mount tail staining. Immune regulation of T-96 in CD8⁺ T cells was evaluated using flow cytometry. Pull-down assay, mass spectrum analysis, molecular docking, knockdown and overexpression approaches were utilized to identify the target proteins of T-96 in CD8⁺ T cells and keratinocytes.

RESULTS

Here, we found that T-96 reduced CD8⁺ T cell infiltration in the epidermis using whole-mount tail staining and alleviated the extent of depigmentation to a comparable degree of tofacitinib (Tofa) in our vitiligo mouse model. In vitro, T-96 decreased the proliferation, CD69 membrane expression, and IFN-γ, granzyme B, (GzmB), and perforin (PRF) levels in CD8⁺ T cells isolated from patients with vitiligo. Pull-down assays combined with mass spectrum analysis and molecular docking showed that T-96 interacted with JAK3 in CD8⁺ T cell lysates. Furthermore, T-96 reduced JAK3 and STAT5 phosphorylation following IL-2 treatment. T-96 could not further reduce IFN-γ, GzmB and PRF expression following JAK3 knockdown or inhibit increased immune effectors expression upon JAK3 overexpression. Additionally, T-96 interacted with JAK2 in IFN-γ-stimulated keratinocytes, inhibiting the activation of JAK2, decreasing the total and phosphorylated protein levels of STAT1, and reducing the production and secretion of CXCL9 and CXCL10. T-96 did not significantly inhibit STAT1 and CXCL9/10 expression following JAK2 knockdown, nor did it suppress upregulated STAT1-CXCL9/10 signaling upon JAK2 overexpression. Finally, T-96 reduced the membrane expression of CXCR3, and the culture supernatants pretreated with T-96 under IFN-γ stressed keratinocytes markedly blocked the migration of CXCR3⁺CD8⁺ T cells, similarly to Tofa in vitro.

CONCLUSION

Our findings demonstrated that T-96 might have positive therapeutic responses to vitiligo by pharmacologically inhibiting the effector functions and skin trafficking of CD8⁺ T cells through JAK-STAT signaling.

CXCL9 Links Skin Inflammation and Fibrosis through CXCR3-Dependent Upregulation of Col1a1 in Fibroblasts

Morphea is characterized by initial inflammation followed by fibrosis of the skin and soft tissue. Despite its substantial morbidity, the pathogenesis of morphea is poorly studied. Previous work showed that CXCR3 ligands CXCL9 and CXCL10 are highly upregulated in the sera and lesional skin of patients with morphea. We found that an early inflammatory subcutaneous bleomycin mouse model of dermal fibrosis mirrors the clinical, histological, and immune dysregulation observed in human morphea. We used this model to examine the role of the CXCR3 chemokine axis in the pathogenesis of cutaneous fibrosis. Using the REX3 (Reporting the Expression of CXCR3 ligands) mice, we characterized which cells produce CXCR3 ligands over time. We found that fibroblasts contribute the bulk of CXCL9-RFP and CXCL10-BFP by percentage, whereas macrophages produce high amounts on a per-cell basis. To determine whether these chemokines are mechanistically involved in pathogenesis, we treated Cxcl9-, Cxcl10-, or Cxcr3-deficient mice with bleomycin and found that fibrosis is dependent on CXCL9 and CXCR3. Addition of recombinant CXCL9 but not CXCL10 to cultured mouse fibroblasts induced Col1a1 mRNA expression, indicating that the chemokine itself contributes to fibrosis. Taken together, our studies provide evidence that CXCL9 and its receptor CXCR3 are functionally required for inflammatory fibrosis.

TMT-Based Quantitative Proteomic and Physiological Analyses on Serums of Chinese Patients with Active Vitiligo

Purpose

Vitiligo is an acquired depigmented skin disorder. Though genetic background, autoimmune dysregulation, and oxidative stress were reported involved in the development of vitiligo, the exact pathogenesis remains largely unknown. This study aimed to investigate potential functional proteins, pathways, and serum biomarkers involved in active vitiligo.

Patients and Methods

Tandem Mass Tags (TMT) method was used to determine differentially expressed proteins (DEPs) in serum samples between 11 active vitiligo patients and 7 healthy controls of Chinese Han population.

Results

A total of 31 DEPs were identified (P < 0.05, fold change >1.2), with 21 proteins upregulated and 10 proteins downregulated in the vitiligo group. DEPs were enriched in GO terms such as "extracellular exosome" and "immunoglobulin receptor binding", as well as KEGG pathways including "cysteine and methionine metabolism" and other immune-related pathways. Furthermore, ALDH1A1 and EEF1G achieved areas under receiver-operating characteristic (ROC) curve of 0.9221 and 0.8571, respectively. The expression levels of these 2 proteins were validated in another active vitiligo patient group.

Conclusion

Our research provided novel insight into serum proteomic profile for vitiligo patients, detecting ALDH1A1 and EEF1G as potential biomarkers for active vitiligo and therapeutic intervention. Our work also detected several DEPs and associated pathways in the serum of active vitiligo patients, reinforcing the roles of retinoic acid and exosome processes in vitiligo pathogenesis.

Aberrant inflammasome activation as a driving force of human autoimmune skin disease

Autoimmune skin diseases are understood as conditions in which the adaptive immune system with autoantigen-specific T cells and autoantibody-producing B cells reacting against self-tissues plays a crucial pathogenic role. However, there is increasing evidence that inflammasomes, which are large multiprotein complexes that were first described 20 years ago, contribute to autoimmune disease progression. The inflammasome and its contribution to the bioactivation of interleukins IL-1β and IL-18 play an essential role in combating foreign pathogens or tissue damage, but may also act as a pathogenic driver of myriad chronic inflammatory diseases when dysfunctionally regulated. Inflammasomes containing the NOD-like receptor family members NLRP1 and NLRP3 as well as the AIM2-like receptor family member AIM2 have been increasingly investigated in inflammatory skin conditions. In addition to autoinflammatory diseases, which are often associated with skin involvement, the aberrant activation of the inflammasome has also been implied in autoimmune diseases that can either affect the skin besides other organs such as systemic lupus erythematosus and systemic sclerosis or are isolated to the skin in humans. The latter include, among others, the T-cell mediated disorders vitiligo, alopecia areata, lichen planus and cutaneous lupus erythematosus as well as the autoantibody-driven blistering skin disease bullous pemphigoid. Some diseases are characterized by both autoinflammatory and autoimmune responses such as the chronic inflammatory skin disease psoriasis. Further insights into inflammasome dysregulation and associated pathways as well as their role in forming adaptive immune responses in human autoimmune skin pathology could potentially offer a new field of therapeutic options in the future.

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.

Targeting the elevated IFN-γ in vitiligo patients by human anti- IFN-γ monoclonal antibody hampers direct cytototoxicity in melanocyte

BACKGROUND

Vitiligo is an autoimmune disease that progressively destroys melanocytes in the skin, resulting in patchy disfiguring depigmentation. The direct pathological effect of IFN-γ, CXCL10 to the melanocytes in vitiligo has been reported, but there are contradictory results to which cytokine exerts the critical cytotoxic effect on melanocytes.

OBJECTIVE

The overarching goal was to study the direct toxicity of highly expressed cytokine in vitiligo skin lesions to melanocytes.

METHODS

We obtained the interstitial fluid analyte from lesion and non-lesion skin of vitiligo patients and healthy control and sent for high sensitivity multiplex cytokine panel. We further performed functional study to identify the direct toxicity effect of the highly expressed cytokines.

RESULTS

We found a significant elevation of IFN-γ, CXCL9, CXCL10, CXCL11 in the vitiligo skin. Ex vivo melanocyte studies support the direct role of IFN-γ per se in melanocyte cell loss, increased oxidative stress and melanogenesis disruption. Interestingly, we found that IFN-γ regulated cell death through oxidative stress-related ferroptosis cell death, which may initiate autoimmunity in vitiligo. In contrast to blocking selected cell death pathway, our in vitro study supports the rescue effect of human anti-IFN-γ monoclonal antibody 2A6Q to IFN-γ induced cell death, oxidative stress, and loss of function in melanocytes by interrupting IFN-γ signaling, which may be a potential therapeutic option for vitiligo.

CONCLUSION

This study further confirms the direct of toxicity effect of IFN-γ per se towards melanocyte in vitiligo skin and the potential utility of human anti-IFN-γ monoclonal antibody in treating vitiligo.

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.

Vitiligo, from Pathogenesis to Therapeutic Advances: State of the Art

Vitiligo is an acquired hypopigmentation of the skin due to a progressive selective loss of melanocytes; it has a prevalence of 1-2% and appears as rounded, well-demarcated white macules. The etiopathology of the disease has not been well defined, but multiple factors contribute to melanocyte loss: metabolic abnormalities, oxidative stress, inflammation, and autoimmunity. Therefore, a convergence theory was proposed that combines all existing theories into a comprehensive one in which several mechanisms contribute to the reduction of melanocyte viability. In addition, increasingly in-depth knowledge about the disease's pathogenetic processes has enabled the development of increasingly targeted therapeutic strategies with high efficacy and fewer side effects. The aim of this paper is, by conducting a narrative review of the literature, to analyze the pathogenesis of vitiligo and the most recent treatments available for this condition.

Systemic therapies in vitiligo: a review

Vitiligo is characterized by the development of depigmented macules and patches. Autoimmunity has been established as a factor in disease pathogenesis, leading to utilization of immunosuppressive agents. Topical immunosuppressants are commonly used; however, this treatment modality is often cumbersome and inefficient, as many patients have active disease with extensive body surface area involvement. Prompt and aggressive treatment of vitiligo is important, as this may prevent progression and improve quality of life. To meet these challenges and improve patient outcomes, interest in systemic therapies has grown. Currently, oral therapies are rarely prescribed, likely due to concerns with systemic side effects and unclear efficacy. This article provides a brief overview on the use of systemic agents in treating vitiligo in order to provide additional therapeutic options to clinicians.

Vitiligo Treatments: Review of Current Therapeutic Modalities and JAK Inhibitors

Vitiligo is a chronic autoimmune disease characterized by loss of pigment of the skin, affecting 0.5-2% of the population worldwide. It can have a significant impact on patients' quality of life. In recent years, there has been significant progress in our understanding of the pathogenesis of vitiligo. It is believed that vitiligo develops due to a complex combination of genetics, oxidative stress, inflammation, and environmental triggers. Conventional treatments include camouflage, topical corticosteroids, topical calcineurin inhibitors, oral corticosteroids, phototherapy, and surgical procedures, with the treatment regimen dependent on the patient's preferences and characteristics. With increased understanding of the importance of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway in the pathogenesis of vitiligo, treatment has expanded to include the first US FDA-approved cream to repigment patients with vitiligo. This review summarizes our understanding of the major mechanisms involved in the pathogenesis of vitiligo and its most common available treatments.

Does immune dysregulation contribute towards development of hypopigmentation in Indian post kala-azar dermal leishmaniasis?

Post kala-azar dermal leishmaniasis (PKDL), a sequel of apparently cured visceral leishmaniasis (VL) presents with papulonodular (polymorphic) or hypopigmented lesions (macular) and is the proposed disease reservoir. As hypopigmentation appears consistently in PKDL, especially the macular form, this study aimed to delineate immune factors that singly or in combination could contribute towards this hypopigmentation. At lesional sites, the presence of melanocytes and CD8⁺ T-cells was assessed by immunohistochemistry and mRNA expression of melanogenic markers (tyrosinase, tyrosinase-related protein-1 and MITF) by droplet digital PCR, while plasma levels of cytokines and chemokines were measured by a multiplex assay. In comparison with skin from healthy individuals, macular PKDL demonstrated a near total absence of Melan-A⁺ cells at dermal sites, while the polymorphic cases demonstrated a 3.2-fold decrease, along with a dramatic reduction in the expression of key enzymes related to the melanogenesis signalling pathway in both forms. The levels of circulating IFN-γ, IL-6, IL-2, IL-1β, TNF-α and IFN-γ-inducible chemokines (CXCL9/10/11) were elevated and was accompanied by an increased lesional infiltration of CD8⁺ T-cells. The proportion of CD8⁺ T-cells correlated strongly with plasma levels of IFN-γ (r = 0.8), IL-6 (r = 0.9, p < 0.05), IL-2 (r = 0.7), TNF-α (r = 0.9, p < 0.05) and IL-1β (r = 0.7), as also with CXCL9 (r = 0.5) and CXCL10 (r = 0.6). Taken together, the absence/reduction in Melan-A suggested hypopigmentation in PKDL was associated with the destruction of melanocytes, following the impairment of the melanogenesis pathway. Furthermore, the presence of CD8⁺ T-cells and an enhanced IFN-γ-associated immune milieu suggested the generation of a pro-inflammatory landscape that facilitated melanocyte dysfunction/destruction.

Exploring Mast Cell-CD8 T Cell Interactions in Inflammatory Skin Diseases

The skin is exposed to environmental challenges and contains skin-resident immune cells, including mast cells (MCs) and CD8 T cells that act as sentinels for pathogens and environmental antigens. Human skin MCs and their mediators participate in the maintenance of tissue homeostasis and regulate the recruitment and activity of immune cells involved in the pathogenesis of skin diseases. The cutaneous CD8 T cell compartment is comprised of long-persisting resident memory T cells (TRM) and migratory or recirculating cells; both populations provide durable site immune surveillance. Several lines of evidence indicate that MC-derived products, such as CCL5 and TNF-α, modulate the migration and function of CD8 T cells. Conversely, activated CD8 T cells induce the upregulation of MC costimulatory molecules. Moreover, the close apposition of MCs and CD8 T cells has been recently identified in the skin of several dermatoses, such as alopecia areata. This review outlines the current knowledge about bidirectional interactions between human MCs and CD8 T cells, analyses the alteration of their communication in the context of three common skin disorders in which these cells have been found altered in number or function-psoriasis, atopic dermatitis, and vitiligo-and discusses the current unanswered questions.

Pathogenic Th2 Cytokine Profile Skewing by IFN-γ-Responding Vitiligo Fibroblasts via CCL2/CCL8

PURPOSE

Vitiligo is a T cell-mediated skin depigmentation disease. Though treatments arresting disease progression and inducing repigmentation are available, the efficacy of these options is often limited and poorly sustained. How stromal signals contribute to the interferon-γ-dominant skin niches is unclear. This study aims to determine how fibroblasts participate in the IFN-γ-dominant vitiligo niche.

PATIENTS AND METHODS

Mouse vitiligo models were established. Fibroblasts from control and vitiligo mice were extracted for RNA sequencing. In vitro IFN-γ stimulation was performed to verify the JAK-STAT pathway by qPCR and Western blot. T cell polarization with chemokines was measured by flow cytometry. Protein levels in tissues were also examined by IHC.

RESULTS

The vitiligo mouse model recapitulates the human CD8-IFN-γ pathway. RNA sequencing revealed elevated chemokine CCL2 and CCL8 in vitiligo fibroblast, which may be regulated by the JAK-STAT signaling. Such phenomenon is verified by JAK inhibitor peficitinib in vitro. Moreover, CCL2 addition into the naïve T polarization system promoted type 2 cytokines secretion, which represents a hallmark of vitiligo lesions.

CONCLUSION

Dermal fibroblasts, a principal constituent of skin structure, respond to IFN-γ by skewing T cells towards a type 2 cytokine profile via CCL2 and CCL8, which can be abrogated by JAK inhibitor peficitinib.

A meta-analysis of chemokines in vitiligo: Recruiting immune cells towards melanocytes

Chemokine research offers insightful information on the pathogenesis of cutaneous immune disorders, such as vitiligo. Compared to cytokines, the higher detectable levels of chemokines display promising potential as future disease biomarkers. Nonetheless, some published study results are contradictory, which can be attributed to patient characteristics and methodological differences. In this study, a meta-analysis was performed to compare chemokine expression in blood and skin samples from vitiligo patients versus healthy controls. Furthermore, the relationship between chemokine expression and disease activity was evaluated. Chemokine levels were investigated in 15 articles in the circulation and in 9 articles in vitiligo skin. Overall, some clear trends were observed. CXCR3 signaling by CXCL10 and CXCL9 has been confirmed by several reports, although CXCL10 showed more robust findings in blood samples. In this meta-analysis, CCL5, CXCL8, CXCL12, and CXCL16 levels were also significantly elevated. This indicates a complex immune pathway activation in vitiligo that overall supports a Th1-dominant response. Chemokines linked to the Th2 and Th17 pathways were less prevalent. Despite these findings, study protocols that examine a broader range of chemokines are encouraged, because current research is mostly focused on a small number of chemokines that were differentially expressed in previous studies.

Review of Ruxolitinib for Treatment of Non-Segmental Vitiligo

OBJECTIVE

To review the pharmacokinetics, efficacy, and safety of topical ruxolitinib for treatment of nonsegmental vitiligo.

DATA SOURCES

Literature published between January 1983 and October 2022 was reviewed from MEDLINE and ClinicalTrials.gov.

STUDY SELECTION AND DATA EXTRACTION

Relevant articles in English and data from clinical trials were included.

DATA SYNTHESIS

In 2 phase II trials, treatment with ruxolitinib cream showed significant improvements in Vitiligo Area Scoring Index (VASI) scores compared with controls. The 1.5% concentration applied twice daily showed the best results after 52 weeks, with 50% VASI improvement in 58% of patients, 75% VASI improvement in 52% of patients, and 90% VASI improvement in 33% of patients. In 2 phase III trials, more patients achieved at least 75% improvement in facial VASI at 24 weeks (primary endpoint; trial 1: 29.9%, trial 2: 29.9%) than controls (trial 1: 7.5% [P < 0.0001], trial 2: 12.9% [P < 0.01]). Common adverse effects were erythema, pruritus, and acne; all events were mild.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE IN COMPARISON TO EXISTING DRUGS

This review summarizes the pharmacokinetics, efficacy, and safety data regarding topical ruxolitinib for vitiligo. Ruxolitinib is associated with significant clinical improvements with low bioavailability and minimal adverse effects compared with conventional topical steroids, calcineurin inhibitors, phototherapy, and depigmentation agents.

CONCLUSIONS

Ruxolitinib cream is the first therapy approved by the Food and Drug Administration for repigmentation of nonsegmental vitiligo. Clinicians should consider these benefits when recommending treatment as conventional therapies may be time-intensive and carry greater risks of adverse effects.

NRF2 in the Epidermal Pigmentary System

Melanogenesis is a major part of the environmental responses and tissue development of the integumentary system. The balance between reduction and oxidation (redox) governs pigmentary responses, for which coordination among epidermal resident cells is indispensable. Here, we review the current understanding of melanocyte biology with a particular focus on the "master regulator" of oxidative stress responses (i.e., the Kelch-like erythroid cell-derived protein with cap'n'collar homology-associated protein 1-nuclear factor erythroid-2-related factor 2 system) and the autoimmune pigment disorder vitiligo. Our investigation revealed that the former is essential in pigmentogenesis, whereas the latter results from unbalanced redox homeostasis and/or defective intercellular communication in the interfollicular epidermis (IFE). Finally, we propose a model in which keratinocytes provide a "niche" for differentiated melanocytes and may "imprint" IFE pigmentation.

DCUN1D1, a new molecule involved in depigmentation via upregulating CXCL10

CD8⁺ T cells in the lesioned site play a crucial role in the pathogenesis of vitiligo. The chemokine CXCL10 secreted by keratinocytes regulates the migration of CD8⁺ T cells into the skin. In our previous study, we found that DCUN1D1 expression in vitiligo lesions positively correlates with Cxcl10 expression. In this study, the regulatory effect of DCUN1D1 on CXCL10 and cell function was investigated. DCUN1D1 protein expression was significantly higher in the skin tissue from vitiligo lesions compared with samples from healthy controls. High expression of DCUN1D1 in keratinocytes caused local hair depigmentation in mice, reduced melanin content, high infiltration of CD8⁺ T cells and increased CXCL10 expression. This suggested that DCUN1D1 may regulate CD8⁺ T-cell infiltration and depigmentation through CXCL10. Inhibition of DCUN1D1 expression in HaCaT cells abolished the IFN-γ-induced upregulation of p-JAK1, p-STAT1 and CXCL10, suppressed the H₂ O₂ -induced ROS generation and apoptosis, and upregulated tyrosinase expression in melanocytes. Collectively, these results show that DCUN1D1 is an important regulator of CXCL10 and may be a new target for the treatment of vitiligo.