Vitiligo, reactive oxygen species and T-cells

Composite Thiophene-Based Nanoparticles: Revisiting the PEDOT:PSS/P3HT Interface for Living-Cell Optical Modulation

Organic semiconducting nanoparticles (NPs) have been attracting increasing attention for their diverse applications in biotechnology, especially as photoactive materials for spatially controlled optical modulation of living-cell functions. Different approaches to optimize their efficacy and reliability have been recently attempted, including control of photophysical/-chemical properties, ad hoc tailoring of materials synthesis, and functionalization with biological moieties. Another promising strategy is offered by the realization of composite light-sensitive NPs, with a supramolecular architecture. This work reports on the fabrication and characterization of polymer NPs based on poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as prototypical examples of fully biocompatible, semiconducting and conducting materials, respectively. This peculiar NP architecture, with conducting islets distributed within the semiconducting phase, translates into optimization of charge dissociation and electron-transfer efficiency, as well as photocurrent generation increase by about an order of magnitude. As an example of relevant physiological interest, effective optical modulation of angiogenesis, driven by NPs, is demonstrated in primary human endothelial cells. The reported strategy is of general validity and broadens the tools available for spatiotemporally controlled, optical modulation of living-cell functions via engineering of the NP architecture and processes at the interface with living cells.

Pterin-Thymidine Adducts: From Their Photochemical Synthesis to Their Photosensitizing Properties

Pterin (Ptr) is the model compound of aromatic pterins, which are efficient photosensitizers present in human skin and are able to oxidize biomolecules upon UVA irradiation. Photosensitization involves chemical alteration of a biomolecule as a result of the initial absorption of radiation by another chemical species, the photosensitizer. Under anaerobic conditions, Ptr reacts with thymine (T) to form photoadducts (T-Ptr). In this work, we present a method to prepare and purify T-Ptr adducts, using 2'-deoxythymidine 5'-monophosphate (dTMP) and single stranded oligonucleotide 5'-d(TTTTT)-3' (dT5), and investigate their photosensitizing properties. Interestingly, the Ptr moiety, when attached to T, retains its photophysical properties. The adduct dTMP-Ptr, upon excitation, forms singlet and triplet excited states, the latter being capable of transferring energy to dissolved O2 and generating singlet oxygen, with an efficiency similar to Ptr. In air-equilibrated solutions, both dTMP-Ptr and dT5-Ptr adducts can photosensitize the oxidation of tryptophan and 2'-deoxyguanosine 5'-monophosphate, two of the main targets of photosensitization in biological systems, with efficiencies close to that of free Ptr. The mechanisms involved in the oxidation of biomolecules can be either type I (electron transfer) or type II (singlet oxygen).

Phototoxic Effects on Skin Biomolecules Induced by a Domestic Nail Polish Dryer Device

UVA radiation and visible light can lead to indirect damage to DNA, proteins, and lipids through photosensitized reactions, where a molecule undergoes a photochemical alteration by the initial absorption of radiation by another molecular entity called photosensitizer (Sens). The chemical changes undergone by biomolecules in photosensitized reactions can trigger important adverse processes such as photoallergy, phototoxicity, and skin cancer, among others. Despite the knowledge about photosensitized reactions and the fact that many endogenous compounds present in the skin can act as Sens, UVA, and visible light are widely used in several devices for domestic and general use without a thorough evaluation of their possible harmful effects; one prominent example is UV-nail polish dryers. The information in the literature about the possible damage that can be caused by using this type of radiation source is controversial. In this work, we demonstrate that the radiation dose emitted by the nail polish dryer device during a typical gel nail manicure session effectively degrades molecules present in the skin under physiological and pathological conditions. Additionally, it may induce damage to biomolecules such as proteins and lipids due to the photosensitization process, leading to the loss of their biological functions.

Caffeic acid derivative WSY6 protects melanocytes from oxidative stress by reducing ROS production and MAPK activation

Purpose

Vitiligo is a chronic depigmentation disease caused by a loss of functioning melanocytes and melanin from the epidermis. Oxidative stress-induced damage to melanocytes is key in the pathogenesis of vitiligo. WSY6 is a caffeic acid derivative synthesized from epigallocatechin-3-gallate (EGCG). This study is to investigate whether the new chemical WSY6 protected melanocytes from H2O2-induced cell damage and to elucidate the underlying molecular mechanism.

Patients and methods

The present study compared the antioxidative potential of WSY6 with EGCG in hydrogen peroxide (H2O2)-treated PIG1 cells. Western blotting was used to study the protein expression of cyto-c, cleaved-caspase3, cleaved-caspase9, and the activation of MAPK family members, including p38, ERK1/2, JNK and their phosphorylation in melanocytes. ROS assay kit to detect intracellular reactive oxygen species production; CCK8 and lactate dehydrogenase leak assay to detect cytotoxicity.

Results

EGCG and WSY6 ameliorated H2O2-induced oxidative stress damage in PIG1 cells in a does-dependent manner, while WSY6 was much more effective. WSY6 reduced cellular ROS production, cytochrome c release, downregulated caspase-3 and caspase-9 activation. MAPK pathway signaling including phosphorylated p38, ERK and JNK were observed under oxidative stress and can be much protected by pre-treatment of WSY6.

Conclusion

These results indicated that WSY6 could be a more powerful antioxidant than EGCG and protect melanocytes against oxidative cytotoxicity.

Antioxidant mechanisms of mesenchymal stem cells and their therapeutic potential in vitiligo

Vitiligo is a skin pigmentation disorder caused by melanocyte damage or abnormal function. Reac-tive oxygen species Reactive oxygen species can cause oxidative stress damage to melanocytes, which in turn induces vitiligo. Traditional treatments such as phototherapy, drugs, and other methods of treatment are long and result in frequent recurrences. Currently, mesenchymal stem cells (MSCs) are widely used in the research of various disease treatments due to their excellent paracrine effects, making them a promising immunoregulatory and tissue repair strategy. Furthermore, an increasing body of evi-dence suggests that utilizing the paracrine functions of MSCs can downregulate oxidative stress in the testes, liver, kidneys, and other affected organs in animal models of certain diseases. Addition-ally, MSCs can help create a microenvironment that promotes tissue repair and regeneration in are-as with oxidative stress damage, improving the disordered state of the injured site. In this article, we review the pathogenesis of oxidative stress in vitiligo and promising strategies for its treatment.

Cutaneous immune-related phenomena in patients with inflammatory arthritides treated with biological therapies: Clinical and pathophysiological considerations

In recent years, identifying the pathophysiologic mechanisms underlying autoimmune arthritides and systematic diseases has led to the use of biological drugs. The primary targets of those biological therapies are cytokines, B cells, and co-stimulation molecules. So far, these targeted therapies have shown good clinical improvement and an acceptable toxicity profile. However, by blocking components of an intact immune system, autoimmune phenomena and paradoxical inflammation have emerged, and among them many cutaneous immune-related adverse events (irAEs). In this article, we review the current state of knowledge on the clinical features and mechanisms of specific cutaneous irAEs observed during treatment with biological therapies. Among those, psoriatic skin lesions are the most commonly observed. Herein, we also report new cases of cutaneous irAEs recently seen in our clinic to help physicians treating inflammatory arthritides recognize cutaneous irAEs early and better manage patients receiving biologic therapies.

Bimodal modulation of in vitro angiogenesis with photoactive polymer nanoparticles

Angiogenesis is a fundamental process in biology, given the pivotal role played by blood vessels in providing oxygen and nutrients to tissues, thus ensuring cell survival. Moreover, it is critical in many life-threatening pathologies, like cancer and cardiovascular diseases. In this context, conventional treatments of pathological angiogenesis suffer from several limitations, including low bioavailability, limited spatial and temporal resolution, lack of specificity and possible side effects. Recently, innovative strategies have been explored to overcome these drawbacks based on the use of exogenous nano-sized materials and the treatment of the endothelial tissue with optical or electrical stimuli. Here, conjugated polymer-based nanoparticles are proposed as exogenous photo-actuators, thus combining the advantages offered by nanotechnology with those typical of optical stimulation. Light excitation can achieve high spatial and temporal resolution, while permitting minimal invasiveness. Interestingly, the possibility to either enhance (≈+30%) or reduce (up to -65%) the angiogenic capability of model endothelial cells is demonstrated, by employing different polymer beads, depending on the material type and the presence/absence of the light stimulus. In vitro results reported here represent a valuable proof of principle of the reliability and efficacy of the proposed approach and should be considered as a promising step towards a paradigm shift in therapeutic angiogenesis.

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.

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.

Kaempferol promotes melanogenesis and reduces oxidative stress in PIG1 normal human skin melanocytes

Vitiligo is an autoimmune disease characterized by depigmentation. Kaempferol is a flavonoid compound with broad anti-inflammatory and antioxidant properties. The purpose of this study was to investigate the effect of kaempferol on melanogenesis in PIG1 normal human skin melanocytes and its response to oxidative stress. The effect of kaempferol on melanin synthesis in PIG1 normal human skin melanocytes was explored by measuring tyrosinase activity, melanin content, mRNA and protein expression of key enzymes and expression of related pathway proteins. The effects of kaempferol pretreatment on cell viability, apoptosis, ROS level and HO-1 protein level under H₂ O₂ stimulation were explored. When treated with kaempferol, the tyrosinase activity and melanin content of PIG1 cells increased, the mRNA and protein expressions of TYR, TRP1, TRP2 and MITF increased, and the phosphorylation level of ERK1/2 increased. Upon the stimulation of H₂ O₂ , kaempferol reduced the production of ROS, decreased apoptosis and increased the protein expression of HO-1 in PIG1 cells. In addition, kaempferol inhibited oxidative stress-induced melanin reduction and promoted melanin synthesis in PIG1 cells and protected against H₂ O₂ -induced oxidative stress damage.

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.

The Role of ABC Transporters in Skin Cells Exposed to UV Radiation

ABC transporters are expressed in skin cells to protect them against harmful xenobiotics. Moreover, these transmembrane proteins have a number of additional functions that ensure skin homeostasis. This review summarizes the current knowledge about the role of specific ABC proteins in the skin, including multi-drug resistance transporters (MDR1/3), the transporter associated with antigen processing 1/2 (TAP1/2), the cystic fibrosis transmembrane conductance regulator (CFTR), sulfonylurea receptors (SUR1/2), and the breast cancer resistance protein (BCRP). Additionally, the effect of UV radiation on ABC transporters is shown. The exposure of skin cells to UV radiation often leads to increased activity of ABC transporters-as has been observed in the case of MDRs, TAPs, CFTR, and BCRP. A different effect of oxidative stress has been observed in the case of mitochondrial SURs. However, the limited data in the literature-as indicated in this article-highlights the limited number of experimental studies dealing with the role of ABC transporters in the physiology and pathophysiology of skin cells and the skin as a whole. At the same time, the importance of such knowledge in relation to the possibility of daily exposure to UV radiation and xenobiotics, used for both skin care and the treatment of its diseases, is emphasized.

Assessment of prostaglandin F2-alpha (PGF2α) in lesional and nonlesional skin of vitiligo patients

BACKGROUND

F2-isoprostane is one of the members of biologically active prostaglandins. It is considered a reliable marker of oxidative stress. This study aimed at investigating and studying the hypothesis of the possible role of prostaglandin F2-alpha (PGF2α) in the pathogenesis of vitiligo and to know if there is a possibility of using it in therapy.

METHODS

This case-control study involved 30 patients with nonsegmental vitiligo and 30 healthy sex- and age-matched controls over a period of 7 months. Skin biopsies were taken from lesional and nonlesional vitiliginous skin of patients and from normal skin of controls for measurement of PGF2α in tissue by ELISA.

RESULTS

The tissue levels of PGF2α in vitiligo patients were significantly higher in both lesional and nonlesional skin than in healthy controls (P < 0.001). The tissue levels of PGF2α in lesional skin were significantly higher than in nonlesional skin (P < 0.001).

CONCLUSION

Based on the fact that PGF2α is a reliable biomarker of oxidative stress, in addition to our results that revealed higher tissue levels of PGF2α in vitiliginous skin than in healthy skin, we can conclude that PGF2α may be incriminated in the pathogenesis of vitiligo. This finding could help in the treatment of this disease by using anti-PGF2α drugs.

Pterin-lysine photoadduct: a potential candidate for photoallergy

Photoallergy is a photosensitivity disorder associated with a modified ability of the skin to react to the combined effect of drugs and sunlight. It has been attributed to the covalent conjugation of proteins with a photosensitizer, yielding modified macromolecules that can act as antigen provoking the immune system response. The potential role of some endogenous compounds as photoallergens has not been fully established. It has been previously proposed that pterins, which are endogenous photosensitizers present in human skin under pathological conditions, are able to covalently bind to proteins. Here, we evaluated the capability of pterin (Ptr) to form photoadducts with free Lysine (Lys) and poly-L-lysine (poly-Lys). The findings obtained using chromatographic and spectroscopic tools, confirm the formation of photoadducts of Ptr with Lys residues. With poly-Lys the resulting adduct retains the spectroscopic properties of the photosensitizer, suggesting that the aromatic Ptr structure is conserved. On the other hand, the photoproduct formed with free Lys does not behave like Ptr, which suggests that if this product is a photoadduct, a chemical modification may have occurred during the photochemical reaction that alters the pterin moiety.

Integrin Regulated Autoimmune Disorders: Understanding the Role of Mechanical Force in Autoimmunity

The pathophysiology of autoimmune disorders is multifactorial, where immune cell migration, adhesion, and lymphocyte activation play crucial roles in its progression. These immune processes are majorly regulated by adhesion molecules at cell–extracellular matrix (ECM) and cell–cell junctions. Integrin, a transmembrane focal adhesion protein, plays an indispensable role in these immune cell mechanisms. Notably, integrin is regulated by mechanical force and exhibit bidirectional force transmission from both the ECM and cytosol, regulating the immune processes. Recently, integrin mechanosensitivity has been reported in different immune cell processes; however, the underlying mechanics of these integrin-mediated mechanical processes in autoimmunity still remains elusive. In this review, we have discussed how integrin-mediated mechanotransduction could be a linchpin factor in the causation and progression of autoimmune disorders. We have provided an insight into how tissue stiffness exhibits a positive correlation with the autoimmune diseases’ prevalence. This provides a plausible connection between mechanical load and autoimmunity. Overall, gaining insight into the role of mechanical force in diverse immune cell processes and their dysregulation during autoimmune disorders will open a new horizon to understand this physiological anomaly.

The involvement of ERK1/2 and p38 MAPK in the premature senescence of melanocytes induced by H2O2 through a p53-independent p21 pathway

BACKGROUND

The pathogenesis of vitiligo is still unknown and oxidative stress is an important factor that can damage or incapacitate melanocytes.

OBJECTIVE

To investigate the role of oxidative stress in the premature senescence of melanocytes and their transfer of melanosomes.

METHODS

Cultured human melanocytes were treated with H₂O₂ after which cell viability and apoptosis were assessed. We investigated whether exposure to H₂O₂ induces premature senescence. RNA sequencing was used to screen aging-related signaling pathways. The expression of dendritic regulatory proteins, adhesion molecules and cell cytoskeletal proteins, as well as melanosome distribution were characterized. The ROS scavenger NAC was used to study the role of ROS in cell senescence and in melanosome transfer.

RESULTS

Cell viability decreased progressively and cell apoptosis increased after treatment with H₂O₂. H₂O₂ treatment tended to induce premature senescence in melanocytes through a p53-independent p21 pathway. RNA sequencing analysis showed that H₂O₂ treatment induced the differential expression of MAPK signaling pathway components. Western blotting and qRT-PCR confirmed that H₂O₂ treatment increased the phosphorylation of ERK1/2 and p38 MAPK, which are involved in inducing the senescence of melanocytes, but not JNK. The expression of cell cytoskeleton and adhesion molecules decreased after H₂O₂ treatment. p21 siRNA treatment reversed these changes. Treatment with NAC improved the premature senescence and the impaired melanosome transfer induced by H₂O₂.

CONCLUSION

H₂O₂ increases ROS levels, which activates the ERK1/2 and p38 MAPK pathways to induce the premature senescence of melanocytes through p21 via a p53-independent pathway and consequently disrupts melanosome transfer.

The Immunogenetics of Vitiligo: An Approach Toward Revealing the Secret of Depigmentation

Vitiligo is a hypomelanotic skin disease and considered to be of autoimmune origin due to breaching of immunological self-tolerance, resulting in inappropriate immune responses against melanocytes. The development of vitiligo includes a strong heritable component. Different strategies ranging from linkage studies to genome-wide association studies are used to explore the genetic factors responsible for the disease. Several vitiligo loci containing the respective genes have been identified which contribute to vitiligo and genetic variants for some of the genes are still unknown. These genes include mainly the proteins that play a role in immune regulation and a few other genes important for apoptosis and regulation of melanocyte functions. Despite the available data on genetic variants and risk alleles which influence the biological processes, only few immunological pathways have been found responsible for all ranges of severity and clinical manifestations of vitiligo. However, studies have concluded that vitiligo is of autoimmune origin and manifests due to complex interactions in immune components and their inappropriate response toward melanocytes. The genes involved in the immune regulation and processing the melanocytes antigen and its presentation can serve as effective immune-therapeutics that can target specific immunological pathways involved in vitiligo. This chapter highlights those immune-regulatory genes involved in vitiligo susceptibility and loci identified to date and their implications in vitiligo pathogenesis.

Photosensitized Dimerization of Tyrosine: The Oxygen Paradox†

In electron-transfer initiated photosensitization processes, molecular oxygen (O₂ ) is not involved in the first bimolecular event, but almost always participates in subsequent steps giving rise to oxygenated products. An exception to this general behavior is the photosensitized dimerization of tyrosine (Tyr), where O₂ does not participate as a reactant in any step of the pathway yielding Tyr dimers (Tyr₂ ). In the pterin (Ptr) photosensitized oxidation of Tyr, O₂ does not directly participate in the formation of Tyr₂ and quenches the triplet excited state of Ptr, the reactive species that initiates the process. However, O₂ is necessary for the dimerization, phenomenon that we have named as the oxygen paradox. Here, we review the literature on the photosensitized formation of Tyr₂ and present results of steady-state and time resolved experiments, in search of a mechanistic model to explain the contradictory role of O₂ in this photochemical reaction system.

Successful Treatment of Vitiligo with Cold Atmospheric Plasma‒Activated Hydrogel

Vitiligo shows insufficient response to current therapies largely owing to T-lymphocyte dysfunction, abnormal inflammatory activation, and excessive oxidative stress in lesions. Cold atmospheric plasma (CAP) possesses pleiotropic antioxidant and anti-inflammatory properties and may offer an improvement to current treatment options. In this study, the efficacy and safety of CAP were investigated in a mouse model of vitiligo and a randomized and controlled trial of patients with active focal vitiligo. Skin biopsies showed that topical treatment of vitiligo-like lesions on mouse dorsal skin by CAP restored the distribution of melanin. In addition, CAP treatment reduced the infiltration of CD11c+ dendritic cells, CD3+ T cells, and CD8+ T cells; inhibited the release of CXCL10 and cytokine IFN-γ; and enhanced cellular resistance to oxidative stress and excessive immune response by enhancing the expression of the transcription factor NRF2 and attenuating the activity of inducible nitric oxide synthase. In a randomized and controlled trial, CAP treatment achieved partial and complete repigmentation in 80% and 20% of vitiligo lesions, respectively, without hyperpigmentation in surrounding areas or other adverse events during the treatment period and its follow-up period. In conclusion, CAP offers a promising option for the management of vitiligo.

Influence of Narrow-Band Ultra Violet B Phototherapy on Homocysteine Status: A Prospective Study of Patients with Different Cutaneous Disorders

Background: Artificial ultraviolet (UV) radiation is a mainstay in the treatment of a variety of inflammatory skin disorders. Despite existence from a wealth of studies on the impact of narrow-band UVB (NBUVB) on serum levels of nutrients, clinical data on its effect on serum homocysteine (HC) level, which is thought to be a risk factor for cardiovascular disorders, dementia, and depression, are scarce. Objective: To assess serum HC status before and after treatment with at least 30 sessions of NBUVB exposure in patients with various cutaneous disorders. Methods: A prospective cohort study was conducted on 39 patients with psoriasis, vitiligo, atopic dermatitis, and mycosis fungoides who underwent at least 30 sessions of NBUVB phototherapy. Serum HC was measured and compared before and after phototherapy. This study was approved by relevant ethics committee. Results: Levels of HC decreased by 24.8% after 30 sessions of NBUVB phototherapy (10.53 ± 3.64 μmol/L vs. 7.92 ± 3.26 μmol/L, p-value <0.0001) and this decrease was more prominent in male participants and patients older than 40 years. Conclusions: Based to our findings, NBUVB phototherapy might be a modality of choice especially for older male patients not only as an effective treatment for cutaneous conditions, but also as a modality with potential protective effects against cardio-cerebro-vascular accidents.

Polymeric nanoparticles containing rapamycin and autoantigen induce antigen-specific immunological tolerance for preventing vitiligo in mice

Vitiligo is an autoimmune disease in which pigment is lost in patches of the skin. CD4⁺ T cells are implicated in vitiligo while regulatory T cells (Tregs) could ameliorate vitiligo. Rapamycin together with autoantigen have been shown to induce immunological tolerance and promote Tregs in multiple autoimmune diseases. In the current study, we synthesized nanoparticles containing rapamycin and autoantigen HEL_46-61 (NP_{HEL46-61/Rapa}) and investigated their effects on vitiligo. We treated bone marrow-derived dendritic cells (BMDCs) from TrpHEL mice with NP_{HEL46-61/Rapa} and monitored the phenotype of BMDCs. We investigated the effects of NP_{HEL46-61/Rapa}-treated BMDCs on CD4⁺ T cell proliferation and differentiation. We administrated NP_{HEL46-61/Rapa} to TCR-TrpHEL mice and investigated the effects on vitiligo. We found that BMDCs can uptake the NP_{HEL46-61/Rapa}, which resulted in decreased expression of costimulation molecules CD80 and CD86 in BMDCs. BMDCs treated with NP_{HEL46-61/Rapa} suppressed antigen-specific CD4⁺ T cell proliferation while promoted the differentiation of these CD4⁺ T cell to Tregs in vitro. Administration of NP_{HEL46-61/Rapa} to TCR-TrpHEL mice ameliorated vitiligo, promoted Treg production, and suppressed IFN-γ and IL-6 production, while induced IL-10 production. Therefore, our study provides experimental evidence that nanoparticles containing rapamycin and autoantigen could induce antigen-specific immunological tolerance and prevent vitiligo.

Effects of a Traditional Caraway Formulation on Experimental Models of Vitiligo and Mechanisms of Melanogenesis

Background

Kursi Karwiya or caraway tablet (CWT), a traditional medicine formula, is widely used in Xinjiang, China, for treating vitiligo, a common autoimmune disease for which there is currently no satisfactory cure. Clinical interventions include pharmacological treatment with psoralens, often in conjunction with UVA radiation, but toxic side effects limit this application. Studies on the activities and mechanisms of CWT are scarce.

Objective

To investigate the in vitro and in vivo effects of CWT in B16 cell line and in animal models of vitiligo, further exploring its mechanisms of regulating melanogenesis.

Methods

Effects of CWT on melanin synthesis in B16 cells and mushroom tyrosinase activity were investigated in vitro. The signaling pathway of melanogenesis in murine B16 melanoma cells was examined by Western blotting. Two different animal models were used, vitiligo induced by hydroquinone in the mouse model and by hydrogen peroxide in the guinea pig model. Relevant biochemical parameters in blood and skin tissue were measured, and visual inspection, histopathology, and immunohistochemical analysis of treated areas were carried out.

Results

CWT produced changes in biochemical parameters including TYR, MDA, MAO, AChE, IL-6, INF-α, β-EP, and cAMP in blood and/or skin tissue and in regulating melanogenesis. After treatment with CTW, skin color, melanin containing hair follicles, and expression of TYR, TRP-1, and TRP-2 in the skin of animals were significantly affected.

Conclusions

CWT alleviated many of detrimental effects in both models of vitiligo. Tyrosinase activity and melanin content in B16 cells were increased, at least in part, via activation of the PKA p38 MAPK signaling pathways. Our results show that CWT produces beneficial effects on parameters of vitiligo and is worthy of further investigation for use in this distressing autoimmune disorder which currently has no effective cure.

Oxidation of tyrosine: Antioxidant mechanism of l-DOPA disclosed

Tyrosine is an amino acid related to crucial physiological events and its oxidation, that produce beneficial or detrimental effects on biological systems, has been extensively studied. Degradation of tyrosine often begins with the loss of an electron in an electron transfer reaction in the presence of a suitable electron acceptor. The reaction is facilitated by excited states of the acceptor in photosensitized processes. Several products of tyrosine oxidation have been described, the main ones being 3,4-dihydroxy-l-phenylalanine (commonly known as DOPA) and tyrosine dimers. Here, we report tyrosine recovery from tyrosyl radical, after one-electron oxidation, in the presence of DOPA. We propose that under high oxidative stress the oxidation of tyrosine may be controlled, in part, by one of its oxidation products. Also, we present strong evidence of antioxidant action of DOPA by preventing tyrosine dimerization, one of the most serious oxidative protein modifications, and the origin of structural modifications leading to the loss of protein functionality.

The relationship between non-segmental Vitiligo, HLA genotype and oxidative stress

BACKGROUND

Vitiligo is an autoimmune disease characterised by acquired loss of melanocytes. Although the pathogenesis of vitiligo remains unknown, oxidative stress and autoimmune dysregulations are considered to play a role.

OBJECTIVE

The aim of this study was to evaluate the HLA profile and total antioxidant capacity (TAC) and their relationship to clinical characteristic of vitiligo patients.

METHODS

Ninety-one vitiligo patients and 100 healthy controls were included in the study. We analysed HLA allele frequencies using sequence-specific oligonucleotide Prob (SSOP) method. Serum total antioxidant capacity (TAC) levels were measured and compared between vitiligo patients and controls.

RESULTS

HLA-A*02 allele frequency was increased (OR = 1.6, CI = 1.12-2.24, P = .009), HLA-A*11 (OR = 0.46, CI = 0.32-0.91, P = .019) and HLA-DRB1*01 (OR = 0.39, CI = 0.16-0.92, P = .029) frequencies were decreased in vitiligo patients. HLA-A*02 allele especially increased the risk of late onset (Vitiligo onset >30 years of age) vitiligo (OR:3.67, 95% CI: 1.63-8.26, P = .002). Serum TAC levels were similar between vitiligo patients and healthy controls but TAC levels were significantly lower in patients who did not have an HLA-DRB1*01 allele (1.52 vs 1.61, P = .033).

CONCLUSION

Our study showed that HLA-A*02 increases, HLA-A*11 and HLA-DRB1*01 decreases vitiligo susceptibility in Turkish patients as well as a possible relationship between HLA and TAC.

Chemical Vitiligo: A Subset of Vitiligo

Chemical leucoderma, an under-diagnosed common condition often mimicking idiopathic vitiligo, represents an acquired depigmentation induced by repeated exposure to specific chemical compounds in subjects with genetic susceptibility to vitiligo. This has been increasing rapidly in incidence in recent decades in developing countries like India. The term 'chemical vitiligo' was first coined by us to indicate the possible relationship between chemical leucoderma and vitiligo, which has been supported recently by other authors to designate the term 'chemical-induced vitiligo'. The largest case series showed that household chemical exposure was the major etiological factor. Causative chemicals are mostly phenolic and catecholic derivatives. Vitiligo pathogenesis is induced by genetic and environmental factors like many other autoimmune diseases. Innate immunity acts as a bridge between cellular stress and adaptive immunity. Multiple patches are commonly seen; children below 12 years are also affected in good numbers. The most common presence of confetti macules indicates these as characteristic, although not pathognomonic, of chemical leucoderma. Chemical leucoderma has been broadened into 'chemical leucoderma syndrome' with proper staging. The clinical criteria for diagnosis of chemical leucoderma have been specifically outlined. Same pathomechanism of chemical leucoderma might elucidate trigger factors and reasons for progression and chronicity in idiopathic vitiligo. Depigmentation in chemical vitiligo spreads to distant sites, in the same way as generalized idiopathic vitiligo. The study showed that chemical triggering factors played a very significant role in the induction and progression of vitiligo. Thus it should be rational to consider chemical vitiligo not as a separate entity but as a major subset of vitiligo spectrum.

Serum levels of miRNA-21-5p in vitiligo patients and effects of miRNA-21-5p on SOX5, beta-catenin, CDK2 and MITF protein expression in normal human melanocytes

BACKGROUND

Epigenetics of vitiligo was evaluated in few studies. In particular, the role of miR-21, a microRNA involved in various processes, including melanogenesis, was never investigated.

OBJECTIVE

Evaluation of serum levels of miR-21-5p in vitiligo patients and miR-21-5p effects on melanogenesis.

METHODS

We measured serum levels of miR-21-5p in 40 patients affected by nonsegmental vitiligo and 40 sex- and age-matched healthy controls. Next, normal human melanocytes were transfected with miR-21-5p to study the effects of this microRNA, which targeted some proteins involved in melanogenesis pathway like SOX5, beta-catenin, cyclin-dependent kinase 2 (CDK2), and MITF.

RESULTS

The expression of miR-21-5p in vitiligo patients was 3.6-4454.4 fold (mean 990.4 ± 1397.9) higher than in controls. The relative expression of miR-21-5p was directly and significantly correlated with disease severity, defined by VASI (Vitiligo Area and Severity Index) score (Rho = 0.89, p = 10^-7), but not other individual or clinical characteristics. In the second part of the study, a significant reduction of SOX5, beta-catenin and CDK2 protein expression and increase of MITF protein expression was observed in cultured melanocytes after 24 h trasfection with miR-21-5p.

CONCLUSION

According to literature, miR-21-5p upregulation and consequent SOX5 downregulation should upregulate melanogenesis, while vitiligo is characterized by skin depigmentation. Our results suggest that current knowledge of the pathogenesis of vitiligo is probably incomplete. Clinical manifestations could result from an altered balance between metabolic pathways with contrasting effects. In this view, miR-21-5p upregulation might be a tentative compensation mechanism. Further studies appear necessary to confirm and better understand our results and their importance.

Therapeutic Potential of Centella asiatica and Its Triterpenes: A Review

Centella asiatica (also known as Centella asiatica (L.) Urb. or Gotu kola) is a traditional Chinese medicine with extensive medicinal value, which is commonly used in Southeast Asian countries. This study aimed to summarize the effects of C. asiatica and its main components on neurological diseases, endocrine diseases, skin diseases, cardiovascular diseases, gastrointestinal diseases, immune diseases, and gynecological diseases, as well as potential molecular mechanisms, to study the pathological mechanism of these diseases based on the changes at the molecular level. The results showed that C. asiatica and its triterpenoids had extensive beneficial effects on neurological and skin diseases, which were confirmed through clinical studies. They exhibited anti-inflammatory, anti-oxidative stress, anti-apoptotic effects, and improvement in mitochondrial function. However, further clinical studies are urgently required due to the low level of evidence and lack of patients.

Efficacy of Topical 5% 5-Fluorouracil with Needling versus 5% 5-Fluorouracil Alone in Stable Vitiligo: A Randomized Controlled Study

Background:

Vitiligo is a chronic disease of great cosmetic concern presenting with depigmented macules and patches. It is often recalcitrant to medical treatment.

Aim:

The aim of the study was to study the efficacy and safety of topical 5% 5-fluorouracil with needling versus topical 5% 5-fluorouracil alone in stable vitiligo.

Materials and Methods:

This interventional prospective study was conducted from July 2018 to June 2019. Total of 60 patients, with stable vitiligo of age older than 10 years, were randomly assigned into two groups of 30 patients each. Group A was treated with needling followed by topical 5% 5-fluorouracil over vitiligo patches. The procedure was performed every 2 weeks for 3 months. Group B was treated with topical 5% 5-fluorouracil alone. Clinical improvement was assessed monthly till 6 months by serial clinical photographs and grading score.

Results:

Initiation of repigmentation started at 1 month in 76 patches (65%) in Group A, whereas in group B, it was seen in 45 patches (38.7%), which was statistically significant (P = 0.0001). Excellent improvement (>75% repigmentation) was noted in 55 patches (47%) in Group A as compared to 5 patches (4.3%) in group B at the end of 6 months (P = 0.03).

Conclusion:

Needling with 5% 5-fluorouracil appears to be simple, safe, and effective treatment in vitiligo. It can be used in poor responders to conventional therapy.

The Influence of Reactive Oxygen Species in the Immune System and Pathogenesis of Multiple Sclerosis

Multiple roles have been indicated for reactive oxygen species (ROS) in the immune system in recent years. ROS have been extensively studied due to their ability to damage DNA and other subcellular structures. Noticeably, they have been identified as a pivotal second messenger for T-cell receptor signaling and T-cell activation and participate in antigen cross-presentation and chemotaxis. As an agent with direct toxic effects on cells, ROS lead to the initiation of the autoimmune response. Moreover, ROS levels are regulated by antioxidant systems, which include enzymatic and nonenzymatic antioxidants. Enzymatic antioxidants include superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase. Nonenzymatic antioxidants contain vitamins C, A, and E, glutathione, and thioredoxin. Particularly, cellular antioxidant systems have important functions in maintaining the redox system homeostasis. This review will discuss the significant roles of ROS generation and antioxidant systems under normal conditions, in the immune system, and pathogenesis of multiple sclerosis.

Childhood vitiligo in Egypt: Clinico-epidemiologic Profile of 483 patients

BACKGROUND

Childhood vitiligo is commonly encountered. Pattern and distribution of childhood vitiligo were not clearly described in past.

AIMS

To study clinical characteristics of vitiligo among Egyptian children in relation to epidemiological data and compare them with those of adolescents and adults.

PATIENTS AND METHODS

Recruited clinically diagnosed vitiligo patients were categorized into three groups: I (children): <12 years old (yo), II (adolescents): 12-18 yo, and III (adults): 18-30 yo. Patients were subjected to history taking, general and dermatological examination to determine skin phototype, type, presentation, and distribution of vitiligo, percentage of body area involved using vitiligo extent score (VES), associated mucosal involvement, presence of leukotrichia, koebnerization, and halo nevi.

RESULTS

A total of 483 vitiligo patients were included: 220 children, 123 adolescents, and 140 adults. The most common form of vitiligo was nonsegmental vitiligo (NSV). Segmental and active vitiligo were more common in children than in adolescents and adults. The most common site of distribution of NSV in children was the face (periocular) vs arms and forearms in adults followed by thighs and legs in both. The mean age of onset of vitiligo in children was 6.18 (SD 2.93) yo, while mean duration of disease was 2.12 (SD 2.21) y. Face was the most common site of onset of vitiligo in children and adolescents vs arms and forearms in adults.

CONCLUSIONS

Childhood vitiligo differs from adult onset vitiligo regarding several features as type, site of onset, distribution, extent, and activity of disease.

Cistanche deserticola polysaccharide induces melanogenesis in melanocytes and reduces oxidative stress via activating NRF2/HO-1 pathway

As a main part of pigmentation disorders, skin depigmentation diseases such as vitiligo and achromic naevus are very common and get more attention now. The pathogenesis of depigmentation includes melanocyte dysfunction and loss, which are possibly caused by heredity, autoimmunity and oxidative stress. Among them, oxidative stress plays a key role; however, few clinical treatments can deal with oxidative stress. As reported, Cistanche deserticola polysaccharide (CDP) is an effective antioxidant; based on that, we evaluated its role in melanocyte and further revealed the mechanisms. In this study, we found that CDP could promote melanogenesis in human epidermal melanocytes (HEMs) and mouse melanoma B16F10 cells, it also induced pigmentation in zebrafish. Furthermore, CDP could activate mitogen‐activated protein kinase (MAPK) signal pathway, then up‐regulated the expression of microphthalmia‐associated transcription factor (MITF) and downstream genes TYR, TRP1, TRP2 and RAB27A. Otherwise, we found that CDP could attenuate H₂O₂‐induced cytotoxicity and apoptosis in melanocytes. Further evidence revealed that CDP could enhance NRF2/HO‐1 antioxidant pathway and scavenge intracellular ROS. In summary, CDP can promote melanogenesis and prevent melanocytes from oxidative stress injury, suggesting that CDP helps maintain the normal status of melanocytes. Thus, CDP may be a novel drug for the treatment of depigmentation diseases.

Comparison of tyrosinase antibody, tyrosinase-related protein-1 and -2 antibodies, melanin-concentrating hormone receptor antibody levels with autologous serum skin test and autologous plasma skin test results in patients with vitiligo

Introduction

Although the exact etiopathogenesis of vitiligo is unknown, the autoimmunity hypothesis is much in evidence. The autologous serum skin test (ASST) and autologous plasma skin test (APST) are in vivo methods used in the diagnosis of some autoimmune diseases, which are easy and inexpensive to perform.

Aim

In this study, we investigated whether or not ASST and APST could determine autoimmunity in patients with vitiligo.

Material and methods

In this study, 30 vitiligo patients presenting to the dermatology outpatient clinic and 30 healthy volunteers without any known autoimmune diseases were included. Antibodies such as tyrosinase, tyrosinase-related protein-1 (TYRP1), tyrosinase-related protein-2 (TYRP2) and melanin-concentrating hormone receptor 1 (MCHR1) antibodies determined to be associated with vitiligo were examined. In addition, the association of these antibodies with the positivity of ASST and APST, which were suggested to be associated with autoimmunity, were examined.

Results

In our study, tyrosinase antibody was found to be significantly higher in vitiligo patients. ASST was positive in 12 (40%) patients with vitiligo and 8 (26.6%) control subjects. APST was positive in 8 (26.6%) of the patients with vitiligo and in 2 (6.6%) of the controls, and there was a significant difference between the groups in terms of APST positivity (p = 0.032). In addition, in our study, a significant correlation was found between TYRP1 antibody positivity and APST positivity in the patient group (p = 0.005).

Conclusions

These findings suggest that we may use APST to investigate the autoimmune etiopathogenesis of vitiligo.

MicroRNA‑155 inhibits the proliferation of CD8+ T cells via upregulating regulatory T cells in vitiligo

It has been reported that loss and degradation of epidermal melanocytes is closely associated with the pathogenesis of vitiligo. In addition, CD8⁺ T and regulatory T (Treg) cells serve an important role during these two processes. MicroRNA-155 (miR-155) is known to contribute to the pathogenesis of vitiligo; however, the mechanism by which miR-155 regulates the development of vitiligo remains unclear. In the present study, naïve T and CD8⁺ T cells were isolated from a patient with non-segmental vitiligo by flow cytometry. The cells were differentiated into Treg cells by treatment with interleukin-2, transforming growth factor-β and retinoic acid. In addition, miR-155 agonists and antagonists were used to investigate the effect of miR-155 on the proliferation of CD8⁺ T cells, Treg cells and melanocytes. The results demonstrated that the miR-155 agonist significantly decreased the rate of CD8⁺ T cell growth, as well as promoted the proliferation of melanocytes by inducing an increase in the percentage of Treg cells. By contrast, the miR-155 antagonist inhibited the proliferation of melanocytes by decreasing the percentage of Treg cells. miR-155 protected melanocyte survival by increasing the number of Treg cells and by decreasing the number of CD8⁺ T cells. Therefore, these data may provide a new prospect for the treatment of vitiligo.

Peripilar "Guttate" Hypopigmentation of the Scalp and Idiopathic Guttate Hypomelanosis in Frontal Fibrosing Alopecia

Frontal fibrosing alopecia (FFA) is characterized by progressive band-like scarring alopecia involving the frontotemporal hairline and limbs and irreversible alopecia of the eyebrows. Two opposite types of pigmentary alterations have been reported in FFA: hyper- and hypopigmentation. Here, we report a 57-year-old Hispanic female with FFA who presented with peripilar hypopigmentation and idiopathic guttate hypomelanosis on the upper extremities. To our knowledge, this is the first report of peripilar white halos in a patient of a White Hispanic origin. Upon review of other previous publications on trichoscopy of FFA, this pattern has not been detected. The common pattern of focal absence of melanocytes and melanin in both is another confirmation that FFA is associated with pigmentation abnormalities.

SIRT3-Dependent Mitochondrial Dynamics Remodeling Contributes to Oxidative Stress-Induced Melanocyte Degeneration in Vitiligo

Mitochondrial dysregulation has been implicated in oxidative stress-induced melanocyte destruction in vitiligo. However, the molecular mechanism underlying this process is merely investigated. Given the prominent role of nicotinamide adenine dinucleotide (NAD⁺)-dependent deacetylase Sirtuin3 (SIRT3) in sustaining mitochondrial dynamics and homeostasis and that SIRT3 expression and activity can be influenced by oxidative stress-related signaling, we wondered whether SIRT3 could play an important role in vitiligo melanocyte degeneration by regulating mitochondrial dynamics.

Methods: We initially testified SIRT3 expression and activity in normal and vitiligo melanocytes via PCR, immunoblotting and immunofluorescence assays. Then, cell apoptosis, mitochondrial function and mitochondrial dynamics after SIRT3 intervention were analyzed by flow cytometry, immunoblotting, confocal laser microscopy, transmission electron microscopy and oxphos activity assays. Chromatin immunoprecipitation (ChIP), co-immunoprecipitation (Co-IP), immunoblotting and immunofluorescence assays were performed to clarify the upstream regulatory mechanism of SIRT3. Finally, the effect of honokiol on protecting melanocytes and the underlying mechanism were investigated via flow cytometry and immunoblotting analysis.

Results: We first found that the expression and the activity of SIRT3 were significantly impaired in vitiligo melanocytes both in vitro and in vivo. Then, SIRT3 deficiency led to more melanocyte apoptosis by inducing severe mitochondrial dysfunction and cytochrome c release to cytoplasm, with Optic atrophy 1 (OPA1)-mediated mitochondrial dynamics remodeling involved in. Moreover, potentiated carbonylation and dampened peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) activation accounted for SIRT3 dysregulation in vitiligo melanocytes. Finally, we proved that honokiol could prevent melanocyte apoptosis under oxidative stress by activating SIRT3-OPA1 axis.

Conclusions: Overall, we demonstrate that SIRT3-dependent mitochondrial dynamics remodeling contributes to oxidative stress-induced melanocyte degeneration in vitiligo, and honokiol is promising in preventing oxidative stress-induced vitiligo melanocyte apoptosis.

Ischemic modified albumin as a new biomarker in predicting oxidative stress in alopecia areata

Background/aim

Results show that oxidative stress is a pathophysiologic factor for alopecia areata (AA); however, the markers used can be confounding. Thus, we aimed to investigate the role of oxidative stress in the pathogenesis of AA through an evaluation of ischemia-modified albumin (IMA); other markers of the oxidant/antioxidant system, such as SOD, CAT, GSH-ST, and MDA; and contributing clinical risk factors.

Materials and methods

The usefulness of IMA as a new marker for oxidative stress was compared with that of other markers and evaluated in patients with AA.

Results

The mean serum level of IMA was of higher statistical significance in AA patients than in the control group (IMA: 0.57 ± 0.01 vs. 0.52 ± 0.02 ΔABSU, P < 0.0001). IMA (P = 0.03, OR = 25.8, 95% CI = 1.4–482.7) was found to be an independent predictor of oxidative stress in patients with AA. Increased severity of AA was found as an independent risk factor for IMA.

Conclusion

Long-lasting disease, male sex, >1 site of involvement of disease, and increased severity of disease were correlated with increased oxidation. Presence of AA, male sex, and severe disease were determined to be independent risk factors for antioxidant and oxidant systems. IMA has great potential as a biomarker of oxidative stress in AA when compared to other studied biomarkers.

Molecular and cellular basis of depigmentation in vitiligo patients

Vitiligo is a chronic skin disease characterized by the appearance of zones of depigmentation. It is mostly described as an autoimmune disease in which the immune system destroys the melanocytes. Consistent with this origin, genetic studies have implicated genes encoding proteins mediating the immune response targeting melanocytes in the aetiology of this disease, together with proteins specific to these cells. However, the destruction of melanocytes by the immune system is neither global nor complete, because the patients do not display total depigmentation. The etiopathology of vitiligo is clearly complex and cannot be simply reduced to an autoimmune reaction directed against pigmented cells. Intrinsic changes have been observed in the melanocytes, keratinocytes and dermal cells of vitiligo patients. Identification of the molecular and cellular changes occurring in normally pigmented skin in vitiligo patients, and an understanding of these changes, is essential to improve the definition of trigger events for this disease, with a view to developing treatments with long-term efficacy. This review focuses on the early events identified to date in the non-lesional regions of the skin in vitiligo patients and discusses the process of repigmentation from melanocyte stem cells.

Photocatalytic Activity of Polymer Nanoparticles Modulates Intracellular Calcium Dynamics and Reactive Oxygen Species in HEK-293 Cells

Optical modulation of living cells activity by light-absorbing exogenous materials is gaining increasing interest, due to the possibility both to achieve high spatial and temporal resolution with a minimally invasive and reversible technique and to avoid the need of viral transfection with light-sensitive proteins. In this context, conjugated polymers represent ideal candidates for photo-transduction, due to their excellent optoelectronic and biocompatibility properties. In this work, we demonstrate that organic polymer nanoparticles, based on poly(3-hexylthiophene) conjugated polymer, establish a functional interaction with an in vitro cell model (Human Embryonic Kidney cells, HEK-293). They display photocatalytic activity in aqueous environment and, once internalized within the cell cytosol, efficiently generate reactive oxygen species (ROS) upon visible light excitation, without affecting cell viability. Interestingly, light-activated ROS generation deterministically triggers modulation of intracellular calcium ion flux, successfully controlled at the single cell level. In perspective, the capability of polymer NPs to produce ROS and to modulate Ca2+ dynamics by illumination on-demand, at non-toxic levels, may open the path to the study of biological processes with a gene-less approach and unprecedented spatio-temporal resolution, as well as to the development of new biotechnology tools for cell optical modulation.

The nuclear factor (erythroid-derived 2)-like 2 (NRF2) antioxidant response promotes melanocyte viability and reduces toxicity of the vitiligo-inducing phenol monobenzone

Vitiligo, characterised by progressive melanocyte death, can be initiated by exposure to vitiligo-inducing phenols (VIPs). VIPs generate oxidative stress in melanocytes and activate the master antioxidant regulator NRF2. While NRF2-regulated antioxidants are reported to protect melanocytes from oxidative stress, the role of NRF2 in the melanocyte response to monobenzone, a clinically relevant VIP, has not been characterised. We hypothesised that activation of NRF2 may protect melanocytes from monobenzone-induced toxicity. We observed that knockdown of NRF2 or NRF2-regulated antioxidants NQO1 and PRDX6 reduced melanocyte viability, but not viability of keratinocytes and fibroblasts, suggesting that melanocytes were preferentially dependent upon NRF2 activity for growth compared to other cutaneous cells. Furthermore, melanocytes activated the NRF2 response following monobenzone exposure and constitutive NRF2 activation reduced monobenzone toxicity, supporting NRF2's role in the melanocyte stress response. In contrast, melanocytes from individuals with vitiligo (vitiligo melanocytes) did not activate the NRF2 response as efficiently. Dimethyl fumarate-mediated NRF2 activation protected normal and vitiligo melanocytes against monobenzone-induced toxicity. Given the contribution of oxidant-antioxidant imbalance in vitiligo, modulation of this pathway may be of therapeutic interest.

NADPH Oxidases and Their Roles in Skin Homeostasis and Carcinogenesis

SIGNIFICANCE

Skin protects the body from dehydration, pathogens, and external mutagens. NADPH oxidases are central components for regulating the cellular redox balance. There is increasing evidence indicating that reactive oxygen species (ROS) generated by members of this enzyme family play important roles in the physiology and pathophysiology of the skin. Recent Advances: NADPH oxidases are active producers of ROS such as superoxide and hydrogen peroxide. Different isoforms are found in virtually all tissues. They play pivotal roles in normal cell homeostasis and in the cellular responses to various stressors. In particular, these enzymes are integral parts of redox-sensitive prosurvival and proapoptotic signaling pathways, in which they act both as effectors and as modulators. However, continuous (re)activation of NADPH oxidases can disturb the redox balance of cells, in the worst-case scenario in a permanent manner. Abnormal NADPH oxidase activity has been associated with a wide spectrum of diseases, as well as with aging and carcinogenesis.

CRITICAL ISSUES

Sunlight with its beneficial and deleterious effects induces the activation of NADPH oxidases in the skin. Evidence for the important roles of this enzyme family in skin cancer and skin aging, as well as in many chronic skin diseases, is now emerging.

FUTURE DIRECTIONS

Understanding the precise roles of NADPH oxidases in normal skin homeostasis, in the cellular responses to solar radiation, and during carcinogenesis will pave the way for their validation as therapeutic targets not only for the prevention and treatment of skin cancers but also for many other skin-related disorders. Antioxid. Redox Signal. 28, 1238-1261.