Vitiligo skin T cells are prone to produce type 1- and type 2-cytokines to induce melanocyte dysfunction and epidermal inflammatory response through JAK signaling

From traditional medicine to nanomedicine: potential of Ginkgo biloba extracts in treating inflammatory skin diseases

The use of plant extracts as a potential cure for various conditions has moved from traditional medicine to evidence-based medicine. Skin diseases have been addressed since time immemorial using plant extracts through observational and traditional knowledge and passed on through generations. With the advent of modern techniques, the molecular mechanisms of action of plant extracts/isolates are being deciphered with more precision, and more nanomedicine-based therapies are being studied to improve their therapeutic efficacy and stability. The leaves and seeds of Ginkgo biloba (G. biloba), an ancient medicinal tree species, have been used in Chinese herbal medicine for thousands of years. G. biloba extracts have been widely studied as a neuroprotective and anti-ischaemic drug for ischaemia-reperfusion injuries in the heart, lungs, brain, kidneys, and other organs. However, the use of G. biloba can be accompanied with side effects and drug interactions. Although, there is now a growing interest for its use in skincare, the mechanisms of action of the extract are not fully understood and vital aspects of G. biloba, such as its neuroprotective and angiogenic properties contributing to the treatment of inflammatory skin diseases and skin ageing, are yet to be investigated. This review critically discusses the mechanisms of action of different constituents of G. biloba extracts linked to their potential interference in the molecular mechanisms underlying the pathogenesis of inflammatory skin diseases. In addition to its ability to act on oxidative stress, G. biloba can regulate angiogenesis through its compounds such as ginkgetin or ginkgolide K, which either inhibit aberrant angiogenesis in eczema/psoriasis or increase microcirculation during skin ageing. G. biloba may also contribute to the control of pruritus in atopic dermatitis via a neuroprotective and anti-inflammatory mechanism by suppressing JAK2/STAT3 signalling pathways. This review also highlights nanomedicine strategies to decrease the side effects and enhance the efficacy of the extracts. Similar strategies have been successfully used for anticancer molecules in targeted chemotherapy and iron delivery in anaemia treatment.

Ritlecitinib, a JAK3/TEC family kinase inhibitor, stabilizes active lesions and repigments stable lesions in vitiligo

The efficacy of ritlecitinib, an oral JAK3/TEC family kinase inhibitor, on active and stable lesions was evaluated in patients with active non-segmental vitiligo in a phase 2b trial (NCT03715829). Patients were randomized to placebo or daily ritlecitinib 50 mg (with or without 4-week 100-mg or 200-mg loading dose), 30 mg, or 10 mg for 24 weeks. Active lesions showed greater baseline expression of inflammatory/immune markers IFNG and CCL5, levels of CD103, and T-cell infiltrates than stable lesions. Patients with more active than stable vitiligo lesions showed higher baseline serum levels of CXCL9 and PD-L1, while patients with more stable than active lesions showed higher baseline serum levels of HO-1. At Week 24, ritlecitinib 50 mg significantly stabilized mean percent change from baseline in depigmentation extent in both active lesions and stable lesions vs. placebo-response, with stable lesions showing greater repigmentation. After 24 weeks of treatment, ritlecitinib 50 mg increased expression of melanocyte markers in stable lesions, while Th1/Th2-related and co-stimulatory molecules decreased significantly in both stable and active lesions. Serum from patients with more active than stable lesions showed decreased levels of ICOS and NK cell activation markers. These data, confirmed at transcription/protein levels, indicate that stable lesion repigmentation occurs early with ritlecitinib, while active lesions require stabilization of inflammation first. ClinicalTrials.gov: NCT03715829.

Circulating immune cells and vitiligo: a bidirectional two-sample Mendelian randomization study

Background

The pathogenesis of vitiligo remains elusive. Emerging evidence suggests that vitiligo is an immune-mediated disorder, in which a plethora of immune cells play pivotal roles. However, the association between circulating immune cells and vitiligo continues to be enigmatic.

Materials and methods

We extracted single nucleotide polymorphisms (SNPs) associated with immune circulating cells at a genome-wide significance level from the BLOOD CELL CONSORTIUM's genome-wide association study (GWAS) dataset. Summary data for 385,801 cases of vitiligo were obtained from a large-scale Finnish genome-wide association study (ncases=292, ncontrols=385,509). The inverse variance weighted (IVW) method was employed as the primary analytical approach for Mendelian randomization (MR) analysis. Additionally, heterogeneity was assessed using Cochran's Q value, and horizontal pleiotropy was evaluated using MR-Egger Mendelian Randomization Pleiotropy RESidual Sum and Outlier and leave-one-out analyses.

Results

The risk of vitiligo was found to increase with the elevation of 4 circulating immune cells, as evidenced by the odds ratios (ORs) and 95% confidence intervals (CIs): basophils (OR=1.81; 95% CI: 1.01-3.24, p=0.0450), monocytes (OR=1.67; 95% CI: 1.23-2.26, p=0.0009), eosinophils (OR=1.78; 95% CI: 1.22-2.59, p=0.0028), and neutrophils (OR=1.65; 95% CI: 1.08-2.54, p=0.0208). After removing outliers, the sensitivity analysis of the above indicators did not show heterogeneity and pleiotropy.

Conclusion

Our findings illuminate the association between circulating immune cells and vitiligo, offering insights that could guide clinical practices in the treatment of vitiligo.

Type-2 immunity associated with type-1 related skin inflammatory diseases: friend or foe?

Chronic inflammatory skin diseases are multifactorial diseases that combine genetic predisposition, environmental triggers, and metabolic disturbances associated with abnormal immune responses. From an immunological perspective, the better understanding of their physiopathology has demonstrated a large complex network of immune cell subsets and related cytokines that interact with both epidermal and dermal cells. For example, in type-1-associated diseases such as alopecia areata, vitiligo, and localized scleroderma, recent evidence suggests the presence of a type-2 inflammation that is well known in atopic dermatitis. Whether this type-2 immune response has a protective or detrimental impact on the development and chronicity of these diseases remains to be fully elucidated, highlighting the need to better understand its involvement for the management of patients. This mini-review explores recent insights regarding the potential role of type-2-related immunity in alopecia areata, vitiligo, and localized scleroderma.

Ruxolitinib Cream 1.5%: A Review in Non-Segmental Vitiligo

Topical ruxolitinib 1.5% cream (Opzelura®), a Janus kinase (JAK) inhibitor, is the first treatment to be approved in several countries for use in patients aged ≥ 12 years with non-segmental vitiligo. In the identical phase III TRuE-V1 and TRuE-V2 trials, significantly more ruxolitinib cream recipients were able to achieve statistically significant and clinically meaningful facial and total body repigmentation, as well as reductions in vitiligo noticeability, compared with vehicle recipients. Efficacy was sustained in longer-term analyses to week 104 of treatment. Ruxolitinib 1.5% cream was generally tolerable in these trials; the most common treatment-related adverse events were acne, pruritus and exfoliation, all at the application site. As with orally administered JAK inhibitors, topical ruxolitinib carries boxed warnings in the USA for serious infections, mortality, malignancy, major adverse cardiovascular events (MACE) and thrombosis, although the incidences were low with topical application. Thus, topical ruxolitinib 1.5% cream is an effective and generally tolerable treatment option for patients aged ≥ 12 years with non-segmental vitiligo.

The role of dermal fibroblasts in autoimmune skin diseases

Fibroblasts are an important subset of mesenchymal cells in maintaining skin homeostasis and resisting harmful stimuli. Meanwhile, fibroblasts modulate immune cell function by secreting cytokines, thereby implicating their involvement in various dermatological conditions such as psoriasis, vitiligo, and atopic dermatitis. Recently, variations in the subtypes of fibroblasts and their expression profiles have been identified in these prevalent autoimmune skin diseases, implying that fibroblasts may exhibit distinct functionalities across different diseases. In this review, from the perspective of their fundamental functions and remarkable heterogeneity, we have comprehensively collected evidence on the role of fibroblasts and their distinct subpopulations in psoriasis, vitiligo, atopic dermatitis, and scleroderma. Importantly, these findings hold promise for guiding future research directions and identifying novel therapeutic targets for treating these diseases.

Resident memory T cells in nonlesional skin and healed lesions of patients with chronic inflammatory diseases: Appearances can be deceptive

Tissue-resident memory T (TRM) cells serve as a first line of defense in peripheral tissues to protect the organism against foreign pathogens. However, autoreactive TRM cells are increasingly implicated in autoimmunity, as evidenced in chronic autoimmune and inflammatory skin conditions. This highlights the need to characterize their phenotype and understand their role for the purpose of targeting them specifically without affecting local immunity. To date, the investigation of TRM cells in human skin diseases has focused mainly on lesional tissues of patients. Accumulating evidence suggests that self-reactive TRM cells are still present in clinically healed lesions of patients and play a role in disease flares, but TRM cells also populate skin that is apparently normal. This review discusses the ontogeny of TRM cells in the skin as well as recent insights regarding the presence of self-reactive TRM cells in both clinically healed skin and nonlesional skin of patients with autoimmune and inflammatory skin conditions, with a particular focus on psoriasis, atopic dermatitis, and vitiligo.

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.

ISG15-USP18 Dysregulation by Oxidative Stress Promotes IFN-γ Secretion from CD8+ T Cells in Vitiligo

Excessive oxidative stress is thought to play pathologic roles in cellular senescence and autoimmune disorders by inducing inflammation and breaking down immune tolerance. In this study, we sought to identify the factors linking oxidative stress to autoimmunity and cellular senescence in vitiligo, where elevated oxidative stress plays an important role. RNA sequencing analysis of hydrogen peroxide-treated melanocytes revealed upregulation of ISG15. The upregulation of ISG15 was observed in vitiligo skin tissues as well as in the blood of patients with vitiligo, whereas USP18 downregulation was observed in vitiligo melanocytes and vitiligo skin tissues. Oxidative stress induced hypermethylation of the USP18 promoter region in keratinocytes and melanocytes, and USP18 promoter hypermethylation was also confirmed in vitiligo skin tissues. Our results indicate that USP18 promoter hypermethylation caused by oxidative stress increases ISG15 expression in keratinocytes and melanocytes along with senescence changes, leading CD8+ T cells to produce IFN-γ, the main pathogenic cytokine in vitiligo. Therefore, the ISG15-USP18 network may be important in oxidative stress-induced autoimmunity and cellular senescence in vitiligo pathogenesis.

The role of aryl hydrocarbon receptor in vitiligo: a review

Vitiligo is an acquired autoimmune dermatosis characterized by patchy skin depigmentation, causing significant psychological distress to the patients. Genetic susceptibility, environmental triggers, oxidative stress, and autoimmunity contribute to melanocyte destruction in vitiligo. Due to the diversity and complexity of pathogenesis, the combination of inhibiting melanocyte destruction and stimulating melanogenesis gives the best results in treating vitiligo. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that can regulate the expression of various downstream genes and play roles in cell differentiation, immune response, and physiological homeostasis maintenance. Recent studies suggested that AhR signaling pathway was downregulated in vitiligo. Activation of AhR pathway helps to activate antioxidant pathways, inhibit abnormal immunity response, and upregulate the melanogenesis gene, thereby protecting melanocytes from oxidative stress damage, controlling disease progression, and promoting lesion repigmentation. Here, we review the relevant literature and summarize the possible roles of the AhR signaling pathway in vitiligo pathogenesis and treatment, to further understand the links between the AhR and vitiligo, and provide new potential therapeutic strategies.

Exploring the causal relationship between inflammatory cytokines and immunoinflammatory dermatoses: a Mendelian randomization study

Objectives

Previous studies have shown that the onset and progression of several immunoinflammatory dermatoses are closely related to specific immune-inflammatory responses. To further assess the causal relationship between 41 inflammatory cytokines and immunoinflammatory dermatoses, we used a Mendelian randomization method.

Methods

Mendelian two-sample randomization utilized inflammatory cytokines from a GWAS abstract containing 8,293 healthy participants as well as psoriasis (4,510 cases and 212,242 controls), atopic dermatitis (7,024 cases and 198,740 controls), and vitiligo (131 cases and 207,482 controls). The causal relationship between exposure and outcome was explored primarily using inverse variance weighting. In addition, multiple sensitivity analyses, including MR-Egger, weighted median, simple model, weighted model, and MR-PRESSO, were simultaneously applied to enhance the final results.

Results

The results showed that in clinical practice, IL-4 and IL-1RA were suggestive indicators of atopic dermatitis risk (OR = 0.878, 95% CI = 0.78-0.99, p = 0.036; OR = 0.902, 95% CI = 0.82-1.00, p = 0.045). SCGF-b was a suggestive indicator of psoriasis risk (OR = 1.095, 95% CI = 1.01-1.18, p = 0.023). IL-4 is a suggestive indicator of vitiligo risk (OR = 2.948, 95% CI = 1.28-6.79, p = 0.011).

Conclusion

Our findings suggest that circulating inflammatory cytokines may play a crucial role in the pathogenesis of chronic skin inflammation. IL-4 and IL-1RA may have inhibitory roles in the risk of developing atopic dermatitis, while SCGF-b may have a promoting role in the risk of developing psoriasis. Furthermore, IL-4 may contribute to the risk of developing vitiligo. These results provide insights into further understanding the mechanisms of chronic skin inflammation and offer new targets and strategies for the prevention and treatment of related diseases.

Improvements in immune/melanocyte biomarkers with JAK3/TEC family kinase inhibitor ritlecitinib in vitiligo

BACKGROUND

Vitiligo is an autoimmune depigmenting disorder with no effective and safe treatments. Its pathogenesis is not fully elucidated.

OBJECTIVE

This substudy of a randomized, double-blind, placebo-controlled phase 2b trial (NCT03715829) evaluated effects of ritlecitinib, an oral JAK3/TEC family kinase inhibitor, on skin and blood biomarkers in participants with nonsegmental vitiligo (NSV).

METHODS

Sixty-five adults with NSV participated in the substudy and received daily treatment for 24 weeks with placebo (n = 14) or ritlecitinib with or without a 4-week loading dose: 200 (loading dose)/50 mg (n = 13), 100/50 mg (n = 12), 50 mg (n = 11), 30 mg (n = 8), or 10 mg (n = 6). Skin (lesional and nonlesional) biopsy samples were obtained at baseline and at 4 and 24 weeks. Changes from baseline to weeks 4 and 24 in skin and blood molecular and cellular biomarkers were evaluated by RNA sequencing, quantitative real-time PCR, proteomic analysis, and flow cytometry.

RESULTS

Ritlecitinib-treated groups showed downregulation of immune biomarkers and upregulation of melanocyte-related markers at weeks 4 and 24 compared to baseline and/or placebo. Significant reductions were seen in CD3+/CD8+ T-cell infiltrates, with significant increases in melanocyte markers (tyrosinase; Melan-A) in NSV lesions in the 50 mg ritlecitinib groups (both P < .05). There was significant, dose-dependent downregulation in T-cell activation, NK, cytotoxic, and regulatory markers in lesional skin (IL-2, IL2-RA, IL-15, CCR7, CD5, CRTAM, NCR1, XCL1, KIR3DL1, FASLG, KLRD; P < .05). TH1 and TH2 markers were also downregulated in lesional skin and blood in a dose-dependent manner (P < .05). Changes in immune biomarkers correlated with clinical response.

CONCLUSIONS

Ritlecitinib significantly downregulated proinflammatory biomarkers and increased melanocyte products in skin and blood of participants with NSV, suggesting its potential in treatment. Ritlecitinib-mediated changes positively correlated with clinical response.

Synthesis, in silico modelling, and in vitro biological evaluation of substituted pyrazole derivatives as potential anti-skin cancer, anti-tyrosinase, and antioxidant agents

Twenty-five azole compounds (P1-P25) were synthesised using regioselective base-metal catalysed and microwave-assisted approaches, fully characterised by high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR), and infrared spectra (IR) analyses, and evaluated for anticancer, anti-tyrosinase, and anti-oxidant activities in silico and in vitro. P25 exhibited potent anticancer activity against cells of four skin cancer (SC) lines, with selectivity for melanoma (A375, SK-Mel-28) or non-melanoma (A431, SCC-12) SC cells over non-cancerous HaCaT-keratinocytes. Clonogenic, scratch-wound, and immunoblotting assay data were consistent with anti-proliferative results, expression profiling therewith implicating intrinsic and extrinsic apoptosis activation. In a mushroom tyrosinase inhibition assay, P14 was most potent among the compounds (half-maximal inhibitory concentration where 50% of cells are dead, IC50 15.9 μM), with activity greater than arbutin and kojic acid. Also, P6 exhibited noteworthy free radical-scavenging activity. Furthermore, in silico docking and absorption, distribution, metabolism, excretion, and toxicity (ADMET) simulations predicted prominent-phenotypic actives to engage diverse cancer/hyperpigmentation-related targets with relatively high affinities. Altogether, promising early-stage hits were identified - some with multiple activities - warranting further hit-to-lead optimisation chemistry with further biological evaluations, towards identifying new skin-cancer and skin-pigmentation renormalising agents.

Protein kinases: drug targets for immunological disorders

Protein kinases play a major role in cellular activation processes, including signal transduction by diverse immunoreceptors. Given their roles in cell growth and death and in the production of inflammatory mediators, targeting kinases has proven to be an effective treatment strategy, initially as anticancer therapies, but shortly thereafter in immune-mediated diseases. Herein, we provide an overview of the status of small molecule inhibitors specifically generated to target protein kinases relevant to immune cell function, with an emphasis on those approved for the treatment of immune-mediated diseases. The development of inhibitors of Janus kinases that target cytokine receptor signalling has been a particularly active area, with Janus kinase inhibitors being approved for the treatment of multiple autoimmune and allergic diseases as well as COVID-19. In addition, TEC family kinase inhibitors (including Bruton's tyrosine kinase inhibitors) targeting antigen receptor signalling have been approved for haematological malignancies and graft versus host disease. This experience provides multiple important lessons regarding the importance (or not) of selectivity and the limits to which genetic information informs efficacy and safety. Many new agents are being generated, along with new approaches for targeting kinases.

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.

Understanding of Pathomechanisms and Clinical Practice for Vitiligo

Vitiligo is a disease caused by the acquired depletion of melanocytes and/or melanocyte precursor cells in response to genetic and environmental factors, resulting in depigmentation of the entire body. It is roughly divided into segmental and non-segmental vitiligo, and it has been found that abnormalities of melanocytes themselves and dysregulation of autoimmune responses to melanocytes are greatly involved in the pathology of non-segmental vitiligo. Segmental vitiligo pathology is largely unknown; however, it has been suggested that it may be caused by skin or melanocyte mosaicism. Treatments for vitiligo include topical therapy, ultraviolet therapy, and surgical transplantation, and it is extremely important to correctly understand the pathology to perform optimal treatment. In recent years, the development of vitiligo treatments using Janus kinase (JAK) inhibitors has progressed rapidly. We herein outline the latest pathology of vitiligo, from general vitiligo treatment to the progress of clinical trials using JAK inhibitors, along with what clinicians should consider in archiving precision medicine, including my own ideas thereon.

JAK-STAT pathway inhibitors in dermatology

The JAK-STAT signaling pathway mediates important cellular processes such as immune response, carcinogenesis, cell differentiation, division and death. Therefore, drugs that interfere with different JAK-STAT signaling patterns have potential indications for various medical conditions. The main dermatological targets of JAK-STAT pathway inhibitors are inflammatory or autoimmune diseases such as psoriasis, vitiligo, atopic dermatitis and alopecia areata; however, several dermatoses are under investigation to expand this list of indications. As JAK-STAT pathway inhibitors should gradually occupy a relevant space in dermatological prescriptions, this review presents the main available drugs, their immunological effects, and their pharmacological characteristics, related to clinical efficacy and safety, aiming to validate the best dermatological practice.

Impact of house dust mite in vitiligo skin: environmental contribution to increased cutaneous immunity and melanocyte detachment

BACKGROUND

Vitiligo is an autoimmune skin disorder characterized by loss of melanocytes. Protease-mediated disruption of junctions between keratinocytes and/or keratinocyte intrinsic dysfunction may directly contribute to melanocyte loss. House dust mite (HDM), an environmental allergen with potent protease activity, contributes to respiratory and gut disease but also to atopic dermatitis and rosacea.

OBJECTIVES

To verify if HDM can contribute to melanocyte detachment in vitiligo and if so, by which mechanism(s).

METHODS

Using primary human keratinocytes, human skin biopsies from healthy donors and patients with vitiligo, and 3D reconstructed human epidermis, we studied the effect of HDM on cutaneous immunity, tight and adherent junction expression and melanocyte detachment.

RESULTS

HDM increased keratinocyte production of vitiligo-associated cytokines and chemokines and increased expression of toll-like receptor (TLR)-4. This was associated with increased in situ matrix-metalloproteinase (MMP)-9 activity, reduced cutaneous expression of adherent protein E-cadherin, increased soluble E-cadherin in culture supernatant and significantly increased number of suprabasal melanocytes in the skin. This effect was dose-dependent and driven by cysteine protease Der p1 and MMP-9. Selective MMP-9 inhibitor, Ab142180, restored E-cadherin expression and inhibited HDM-induced melanocyte detachment. Keratinocytes from patients with vitiligo were more sensitive to HDM-induced changes than healthy keratinocytes. All results were confirmed in a 3D model of healthy skin and in human skin biopsies.

CONCLUSIONS

Our results highlight that environmental mite may act as an external source of pathogen-associated molecular pattern molecules in vitiligo and topical MMP-9 inhibitors may be useful therapeutic targets. Whether HDM contributes to the onset of flares in vitiligo remains to be tested in carefully controlled trials.

JAK inhibitors in vitiligo: what they hit and what they miss - an immunopathogenesis based exposition of existing evidence

INTRODUCTION

Vitiligo is an autoimmune disorder which presents as depigmented macules due to selective loss of melanocytes. Heightened expression of Janus Kinase Signal transducers and activators of transcription (JAK STAT) pathway, which mediate cytokines action, suggest that targeting this signaling pathway may be an effective option.

AREAS COVERED

A PubMed search was carried out with the broad key words 'JAK,' 'vitiligo' from 2016 to 2023. We also analyzed papers where tissue-based JAK expression was studied, with or without concomitant treatment with JAK inhibitors. We address the role of JAK inhibitors in vitiligo and their effect on repigmentation of lesions.

EXPERT OPINION

While JAK inhibitors help in cessation of disease progression, they have no in vivo action on melanocyte proliferation and hence cannot result in re-pigmentation as a monotherapy. There is a need for tissue-based JAK and cytokine-based studies with post-treatment expression data to validate the role of this class of drugs in vitiligo. There is as yet no data to suggest that selective JAK inhibitors are superior to pan JAK inhibitors for vitiligo. JAK inhibitors are useful in active disease and effectively modulate the cytokine mediated autoimmune dammage and makes them singularly superior to oral glucocorticosteroids.

Functional heterogeneity of human skin-resident memory T cells in health and disease

The human skin is populated by a diverse pool of memory T cells, which can act rapidly in response to pathogens and cancer antigens. Tissue-resident memory T cells (TRM ) have been implicated in range of allergic, autoimmune and inflammatory skin diseases. Clonal expansion of cells with TRM properties is also known to contribute to cutaneous T-cell lymphoma. Here, we review the heterogeneous phenotypes, transcriptional programs, and effector functions of skin TRM . We summarize recent studies on TRM formation, longevity, plasticity, and retrograde migration and contextualize the findings to skin TRM and their role in maintaining skin homeostasis and altered functions in skin disease.

Mitophagy and immune infiltration in vitiligo: evidence from bioinformatics analysis

Background

Vitiligo is an acquired, autoimmune, depigmented skin disease with unclear pathogenesis. Mitochondrial dysfunction contributes significantly to vitiligo, and mitophagy is vital for removing damaged mitochondria. Herein, using bioinformatic analysis, we sought to determine the possible role of mitophagy-associated genes in vitiligo and immune infiltration.

Methods

Microarrays GSE53146 and GSE75819 were used to identify differentially expressed genes (DEGs) in vitiligo. By crossing vitiligo DEGs with mitophagy-related genes, the mitophagy-related DEGs were identified. Functional enrichment and protein-protein intersection (PPI) analyses were conducted. Then, the hub genes were identified using two machine algorithms, and receiver operating characteristic (ROC) curves were generated. Next, the immune infiltration and its connection with hub genes in vitiligo were investigated. Finally, the Regnetwork database and NetworkAnalyst were used to predict the upstream transcriptional factors (TFs), microRNAs (miRNAs), and the protein-compound network.

Results

A total of 24 mitophagy-related genes were screened. Then, five mitophagy hub genes (GABARAPL2, SP1, USP8, RELA, and TBC1D17) were identified using two machine learning algorithms, and these genes showed high diagnostic specificity for vitiligo. The PPI network showed that hub genes interacted with each other. The mRNA expression levels of five hub genes were validated in vitiligo lesions by qRT-PCR and were compatible with the bioinformatic results. Compared with controls, the abundance of activated CD4⁺ T cells, CD8⁺ T cells, immature dendritic cells and B cells, myeloid-derived suppressor cells (MDSCs), gamma delta T cells, mast cells, regulatory T cells (Tregs), and T helper 2 (Th2) cells was higher. However, the abundance of CD56 bright natural killer (NK) cells, monocytes, and NK cells was lower. Correlation analysis revealed a link between hub genes and immune infiltration. Meanwhile, we predicted the upstream TFs and miRNAs and the target compounds of hub genes.

Conclusion

Five hub mitophagy-related genes were identified and correlated with immune infiltration in vitiligo. These findings suggested that mitophagy may promote the development of vitiligo by activating immune infiltration. Our study might enhance our comprehension of the pathogenic mechanism of vitiligo and offer a treatment option for 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.

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.

Two Phase 3, Randomized, Controlled Trials of Ruxolitinib Cream for Vitiligo

BACKGROUND

Vitiligo is a chronic autoimmune disease that causes skin depigmentation. A cream formulation of ruxolitinib (an inhibitor of Janus kinase 1 and 2) resulted in repigmentation in a phase 2 trial involving adults with vitiligo.

METHODS

We conducted two phase 3, double-blind, vehicle-controlled trials (Topical Ruxolitinib Evaluation in Vitiligo Study 1 [TRuE-V1] and 2 [TRuE-V2]) in North America and Europe that involved patients 12 years of age or older who had nonsegmental vitiligo with depigmentation covering 10% or less of total body-surface area. Patients were randomly assigned in a 2:1 ratio to apply 1.5% ruxolitinib cream or vehicle control twice daily for 24 weeks to all vitiligo areas on the face and body, after which all patients could apply 1.5% ruxolitinib cream through week 52. The primary end point was a decrease (improvement) of at least 75% from baseline in the facial Vitiligo Area Scoring Index (F-VASI; range, 0 to 3, with higher scores indicating a greater area of facial depigmentation), or F-VASI75 response, at week 24. There were five key secondary end points, including improved responses on the Vitiligo Noticeability Scale.

RESULTS

A total of 674 patients were enrolled, 330 in TRuE-V1 and 344 in TRuE-V2. In TRuE-V1, the percentage of patients with an F-VASI75 response at week 24 was 29.8% in the ruxolitinib-cream group and 7.4% in the vehicle group (relative risk, 4.0; 95% confidence interval [CI], 1.9 to 8.4; P<0.001). In TRuE-V2, the percentages were 30.9% and 11.4%, respectively (relative risk, 2.7; 95% CI, 1.5 to 4.9; P<0.001). The results for key secondary end points showed superiority of ruxolitinib cream over vehicle control. Among patients who applied ruxolitinib cream throughout 52 weeks, adverse events occurred in 54.8% in TRuE-V1 and 62.3% in TRuE-V2; the most common adverse events were application-site acne (6.3% and 6.6%, respectively), nasopharyngitis (5.4% and 6.1%), and application-site pruritus (5.4% and 5.3%).

CONCLUSIONS

In two phase 3 trials, application of ruxolitinib cream resulted in greater repigmentation of vitiligo lesions than vehicle control through 52 weeks, but it was associated with acne and pruritus at the application site. Larger and longer trials are required to determine the effect and safety of ruxolitinib cream in patients with vitiligo. (Funded by Incyte; TRuE-V1 and TRuE-V2 ClinicalTrials.gov numbers, NCT04052425 and NCT04057573.).