The Formation of Melanocyte Apoptotic Bodies in Vitiligo and the Relocation of Vitiligo Autoantigens under Oxidative Stress

Human Mesenchymal Stem Cell-Derived Exosomes Promote the Proliferation and Melanogenesis of Primary Melanocytes by Attenuating the H2O2-Related Cytotoxicity in vitro

Background

Mesenchymal stem cell-derived exosomes (MSC-Exo) have therapeutic potential. However, the impact of MSC-Exo on the survival and melanogenesis of human primary melanocytes following H2O2-induced damage has not been clarified. We therefore investigated the effects of MSC-Exo on the H2O2-affected survival of human primary melanocytes and their proliferation, apoptosis, senescence, and melanogenesis in vitro.

Methods

MSC-Exo were prepared from human MSCs by sequential centrifugations and characterized by Transmission Electron Microscopy, Western blot and Nanoparticle Tracking Analysis. Human primary melanocytes were isolated and treated with different concentrations of MSC-Exo, followed by exposing to H2O2. Furthermore, the impact of pretreatment with MSC-Exo on the proliferation, apoptosis, senescence and melanogenesis of melanocytes were tested by CCK-8, flow cytometry, Western blot, L-Dopa staining, tyrosinase activity and RT-qPCR.

Results

Pretreatment with lower doses of MSC-Exo protected human primary melanocytes from the H2O2-triggered apoptosis, while pretreatment with higher doses of MSC-Exo enhanced the H2O2-induced melanocyte apoptosis. Compared with the untreated control, pretreatment with a lower dose (1 µg/mL) of MSC-Exo enhanced the proliferation of melanocytes, abrogated the H2O2-increased p53, p21, IL-1β, IL-6 and IL-8 expression and partially rescued the H2O2-decreased L-dopa staining reaction, tyrosinase activity, MITF and TRP1 expression in melanocytes.

Conclusion

Our findings indicate that treatment with a low dose of MSC-Exo promotes the proliferation and melanogenesis of human primary melanocytes by ameliorating the H2O2-induced apoptosis and senescence of melanocytes. MSC-Exo may be a promising therapeutic strategy of vitiligo.

Identification of TNF-α as Major Susceptible Risk Locus for Vitiligo: A Systematic Review and Meta-Analysis Study in the Asian Population

INTRODUCTION

Vitiligo is a common depigmentation disorder characterized by defined white patches on the skin and affecting around 0.5% to 2% of the general population. Genetic association studies have identified several pre-disposing genes and single nucleotide polymorphisms (SNPs) for vitiligo pathogenesis; nonetheless, the reports are often conflicting and rarely conclusive. This comprehensive meta-analysis study was designed to evaluate the effect of the risk variants on vitiligo aetiology and covariate stratified vitiligo risk in the Asian population, considering all the studies published so far.

METHODS

We followed a systematic and comprehensive search to identify the relevant vitiligo-related candidate gene association studies in PubMed using specific keywords. After data extraction, we calculated, for the variants involved, the study-level unadjusted odds ratio, standard errors, and 95% confidence intervals by using logistic regression with additive, dominant effect, and recessive models using R software package (R, 3.4.2) "metafor." Subgroup analysis was performed using logistic regression (generalized linear model; "glm") of disease status on subgroup-specific genotype counts. For a better understanding of the likely biological function of vitiligo-associated variant obtained through the meta-analysis, in silico functional analyses, through standard publicly available web tools, were also conducted.

RESULTS

Thirty-one vitiligo-associated case-control studies on eleven SNPs were analysed in our study. In the fixed-effect meta-analysis, one variant upstream of TNF-α gene: rs1800629 was found to be associated with vitiligo risk in the additive (p = 4.26E-06), dominant (p = 1.65E-7), and recessive (p = 0.000453) models. After Benjamini-Hochberg false discovery rate (FDR) correction, rs1800629/TNF-α was found to be significant at 5% FDR in the dominant (padj = 1.82E-6) and recessive models (padj = 0.0049). In silico characterization revealed the prioritized variant to be regulatory in nature and thus having potential to contribute towards vitiligo pathogenesis.

CONCLUSION

Our study constitutes the first comprehensive meta-analysis of candidate gene-based association studies reported in the whole of the Asian population, followed by an in silico analysis of the vitiligo-associated variant. According to the findings of our study, TNF-α single nucleotide variant rs1800629G>A has a risk association, potentially contributing to vitiligo pathogenesis in the Asian population.

Advances in biological functions and applications of apoptotic vesicles

BACKGROUND

Apoptotic vesicles are extracellular vesicles generated by apoptotic cells that were previously regarded as containing waste or harmful substances but are now thought to play an important role in signal transduction and homeostasis regulation.

METHODS

In the present review, we reviewed many articles published over the past decades on the subtypes and formation of apoptotic vesicles and the existing applications of these vesicles.

RESULTS

Apoptotic bodies were once regarded as vesicles released by apoptotic cells, however, apoptotic vesicles are now regarded to include apoptotic bodies, apoptotic microvesicles and apoptotic exosomes, which exhibit variation in terms of biogenesis, sizes and properties. Applications of apoptotic vesicles were first reported long ago, but such reports have been rarer than those of other extracellular vesicles. At present, apoptotic vesicles have been utilized mainly in four aspects, including in direct therapeutic applications, in their engineering as carriers, in their construction as vaccines and in their utilization in diagnosis.

CONCLUSION

Building on a deeper understanding of their composition and characteristics, some studies have utilized apoptotic vesicles to treat diseases in more novel ways. However, their limitations for clinical translation, such as heterogeneity, have also emerged. In general, apoptotic vesicles have great application potential, but there are still many barriers to overcome in their investigation. Video Abstract.

Apoptotic bodies: bioactive treasure left behind by the dying cells with robust diagnostic and therapeutic application potentials

Apoptosis, a form of programmed cell death, is essential for growth and tissue homeostasis. Apoptotic bodies (ApoBDs) are a form of extracellular vesicles (EVs) released by dying cells in the last stage of apoptosis and were previously regarded as debris of dead cells. Recent studies unraveled that ApoBDs are not cell debris but the bioactive treasure left behind by the dying cells with an important role in intercellular communications related to human health and various diseases. Defective clearance of ApoBDs and infected-cells-derived ApoBDs are possible etiology of some diseases. Therefore, it is necessary to explore the function and mechanism of the action of ApoBDs in different physiological and pathological conditions. Recent advances in ApoBDs have elucidated the immunomodulatory, virus removal, vascular protection, tissue regenerative, and disease diagnostic potential of ApoBDs. Moreover, ApoBDs can be used as drug carriers enhancing drug stability, cellular uptake, and targeted therapy efficacy. These reports from the literature indicate that ApoBDs hold promising potential for diagnosis, prognosis, and treatment of various diseases, including cancer, systemic inflammatory diseases, cardiovascular diseases, and tissue regeneration. This review summarizes the recent advances in ApoBDs-related research and discusses the role of ApoBDs in health and diseases as well as the challenges and prospects of ApoBDs-based diagnostic and therapeutic applications.

TYRP1 Protects Against the Apoptosis and Oxidative Stress of Retinal Ganglion Cells by Binding to PMEL

OBJECTIVES

This research aimed to dissect the function of TYRP1 and PMEL in glaucomatous animal and cell models.

METHODS

A chronic ocular hypertension (COH) rat model was induced in the right eyes of rats through the electrocoagulation of superficial iris veins. In addition, an oxygen-glucose deprivation (OGD)-retinal ganglion cell (RGC) model was constructed through OGD. TYRP1 and PMEL expression was altered in the animal and cell models to explore their effects.

RESULTS

TYRP1 and PMEL expression was poor in glaucoma patients, COH rats, and OGD-RGCs. Mechanistically, TYRP1 interacted with PMEL to upregulate PMEL in OGD-RGCs. TYRP1 overexpression enhanced viability and diminished apoptosis and oxidative stress of OGD-RGCs, which was abolished by PMEL knockdown. TYRP1 upregulation reduced intraocular pressure, RGC apoptosis, and oxidative stress in COH rats, which was reversed by PMEL knockdown.

CONCLUSIONS

TYRP1 elevates PMEL expression to reduce RGC apoptosis and oxidative stress in vivo and in vitro.

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.

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

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

Heat Shock Protein 90 (Hsp90) and Hsp70 as Potential Therapeutic Targets in Autoimmune Skin Diseases

Over a hundred different autoimmune diseases have been described to date, which can affect every organ in the body, including the largest one, the skin. In fact, up to one-fifth of the world's population suffers from chronic, noninfectious inflammatory skin diseases, the development of which is significantly influenced by an autoimmune response. One of the hallmarks of autoimmune diseases is the loss of immune tolerance, which leads to the formation of autoreactive lymphocytes or autoantibodies and, consequently, to chronic inflammation and tissue damage. The treatment of autoimmune skin diseases mainly focuses on immunosuppression (using, e.g., corticosteroids) but almost never leads to the development of permanent mechanisms of immune tolerance. In addition, current therapies and their long-term administration may cause serious adverse effects. Hence, safer and more effective therapies that bring sustained balance between pro- and anti-inflammatory responses are still desired. Both intra- and extracellular heat shock proteins (Hsps), specifically well-characterized inducible Hsp90 and Hsp70 chaperones, have been highlighted as therapeutic targets for autoimmune diseases. This review presents preclinical data on the involvement of Hsp90 and Hsp70 in modulating the immune response, specifically in the context of the treatment of selected autoimmune skin diseases with emphasis on autoimmune bullous skin diseases and psoriasis.

Targets Exploration of Hydroxychloroquine for Pigmentation and Cell Protection Effect in Melanocytes: The Clue for Vitiligo Treatment

Objective

The treatment of vitiligo is often challenging to dermatologists. There is ample evidence to suggest that hydroxychloroquine (HCQ) is effective for vitiligo treatment; nonetheless, the underlying mechanism remains unknown. In the present study, we sought to uncover the molecular targets of HCQ by an integrated network-based pharmacologic and transcriptomic approach.

Methods

The potential targets of HCQ were retrieved from databases based on the crystal structure. Targets related to vitiligo were screened and intersected with potential targets of HCQ. A protein-protein interaction network of the intersected targets was generated. Interactions between the targets were verified by molecular docking. Moreover, human vitiligo immortalized melanocytes (PIG3V) were evaluated after treatment with HCQ (1μg/mL) for 24h. The total RNA of PIG3V was extracted and determined by RNA-seq transcriptomics for differential gene expression analysis. Network pharmacology was then used to identify the relationships between putative targets of HCQ and differentially expressed genes.

Results

Molecular docking analysis revealed four putative key targets (ACHE, PNMT, MC₁R, and VDR) of HCQ played important roles in vitiligo treatment. According to the transcriptomic results, the melanosomal biogenesis-related gene BLOC1S5 was upregulated 138005.020 fold after HCQ treatment. Genes related to protein repair (MSRB3) and anti-ultraviolet (UV) effect (UVSSA) were upregulated 4.253 and 2.603 fold, respectively, after HCQ treatment.

Conclusion

The expression of the BLOC1S5 gene is significantly upregulated, indicating upregulated melanosomal biogenesis after HCQ treatment. In addition, HCQ yields a protective effect on melanocytes by upregulating genes associated with damaged protein repair (MSRB3) and anti-UV effect (UVSSA). The protective effects of HCQ are mediated by binding to putative targets ACHE, PNMT, MC₁R, and VDR according to network pharmacology and docking verification.