Enhanced DNA binding capacity on up‐regulated epidermal wild‐type p53 in vitiligo by H 2 O 2 ‐mediated oxidation: a possible repair mechanism for DNA damage

The Risk of Keratinocyte Cancer in Vitiligo and the Potential Mechanisms Involved

Although light skin types are associated with increased skin cancer risk, a lower incidence of both melanoma and nonmelanoma skin cancer (NMSC) has been reported in patients with vitiligo. We performed a systematic review and meta-analysis on the NMSC risk in patients with vitiligo, indicating a reduced relative risk ratio of NMSC in vitiligo. Furthermore, we propose a series of hypotheses on the underlying mechanisms, including both immune-mediated and nonimmune-mediated pathways. This study reveals insights into the relationship between vitiligo and keratinocyte cancer and can also be used to better inform patients with vitiligo.

Exploring the mechanism of Liuwei Dihuang formula for promoting melanin synthesis in juvenile zebrafish based on network pharmacology and molecular docking

Background

Vitiligo stands as a challenging skin disorder with limited treatment options available. LiuWei DiHuang formula (LDF), a renowned Traditional Chinese medicine, has exhibited promising results in treating vitiligo over an extended period. However, the precise underlying mechanism of its action remains elusive.

Methods

Employing a comprehensive network pharmacology approach, this study identified active compounds and their corresponding targets within LDF, while also pinpointing vitiligo-associated targets sourced from the TCMSP database, OMIM, DisGenNET, and Genecards. A network was established to illustrate the connections between active compounds and targets, alongside a protein-protein interaction network. Further analyses, encompassing Gene Ontology (GO) function and KEGG pathway enrichment, were conducted using the DAVID platform. Molecular docking simulations were performed utilizing AutoDockTools and AutoDockVina software. To validate the outcomes of the systematic pharmacological investigation, experiments were conducted using juvenile zebrafish.

Results

The collective effort of the network pharmacology approach yielded a compilation of 41 compounds and 192 targets. Molecular docking simulations notably revealed the lowest binding energies for CAT-quercetin and CAT-Kaempferol interactions. The utilization of juvenile zebrafish experiments highlighted a significant increase in melanocyte count following methoxsalen and LDF treatment. Notably, LDF prominently augmented the expression levels of proteins related to melanogenesis. Additionally, LDF showcased the capacity to enhance CAT and SOD levels while concurrently reducing ROS and MDA activity. In contrast to the model group, substantial increases in protein and mRNA levels of Nrf2 and HO-1 were observed in response to LDF treatment (P < 0.05).

Conclusion

Through a meticulous network pharmacology approach, this study successfully predicted active components and potential targets associated with LDF's application in vitiligo treatment. The therapeutic effectiveness of LDF against vitiligo is postulated to stem from its regulation of oxidative stress factors and the Nrf2/HO-1 pathway.

Incidence of skin malignancies in patients with vitiligo or psoriasis who received narrowband ultraviolet B phototherapy (308 nm/311 nm): A retrospective review of 3730 patients

BACKGROUND

Previous studies regarding the risk of skin malignancy with NBUVB have been performed in Caucasian patients, but few studies have been conducted in Asians.

AIM

The aim of the study was to determine the risk of skin cancer in Asian patients with psoriasis and vitiligo receiving NBUVB phototherapy.

METHODS

We performed a 9-year retrospective study including all patients with psoriasis and vitiligo receiving NBUVB (either 311 nm wavelength through cabin phototherapy or 308 nm through excimer lamp phototherapy) at the National Skin Centre. We matched the identification numbers of patients to the National Registry of Diseases Office database and collected data on all skin cancers diagnosed.

RESULTS

A total of 3730 patients were included. During the course of the study, 12 cases of skin cancer were diagnosed, of which 10 were basal cell carcinomas, and 2 were squamous cell carcinomas. No cases of melanoma were detected in the study. The age-standardized incidence of skin cancer in psoriasis and vitiligo patients who received phototherapy was 47.5 and 26.5, respectively, which is higher than the incidence of skin cancers in the general population. Risk of skin malignancy was positively correlated with the cumulative (p = .008) and maximum dose of phototherapy (p = .011) as well as previous systemic treatments (p = .006).

LIMITATIONS

Limitations include a relatively short follow-up period as well as the lack of quantification of solar exposure.

CONCLUSIONS

NBUVB phototherapy in Asian skin increases the risk of skin malignancy. The risk of skin malignancy is higher with psoriasis patients, greater cumulative and maximal dose of phototherapy as well as the use of systemic therapy. Despite the increased risk, the absolute number of skin malignancies remains low, especially for vitiligo patients, with no cases of melanoma diagnosed-a reassuring finding that phototherapy remains a safe alternative in the treatment of psoriasis and vitiligo.

Carrier Free Photodynamic Synergists for Oxidative Damage Amplified Tumor Therapy

Tumor cells adapt to excessive oxidative stress by actuating reactive oxygen species (ROS)-defensing system, leading to a resistance to oxidation therapy. In this work, self-delivery photodynamic synergists (designated as PhotoSyn) are developed for oxidative damage amplified tumor therapy. Specifically, PhotoSyn are fabricated by the self-assembly of chlorine e6 (Ce6) and TH588 through π-π stacking and hydrophobic interactions. Without additional carriers, nanoscale PhotoSyn possess an extremely high drug loading rate (up to 100%) and they are found to be fairly stable in aqueous phase with a uniform size distribution. Intravenously injected PhotoSyn prefer to accumulate at tumor sites for effective cellular uptake. More importantly, TH588-mediated MTH1 inhibition could destroy the ROS-defensing system of tumor cells by preventing the elimination of 8-oxo-2'-deoxyguanosine triphosphate (8-oxo-dG), thereby exacerbating the oxidative DNA damage induced by the photodynamic therapy (PDT) of Ce6 under light irradiation. As a consequence, PhotoSyn exhibit enhanced photo toxicity and a significant antitumor effect. This amplified oxidative damage strategy improves the PDT efficiency with a reduced side effect by increasing the lethality of ROS without generating superabundant ROS, which would provide a new insight for developing self-delivery nanoplatforms in photodynamic tumor therapy in clinic.

Alterations of the pigmentation system in the aging process

Human skin aging is a natural phenomenon that results from continuous exposure to intrinsic (time, genetic factors, hormones) as well as extrinsic factors (UV exposure, pollution, tobacco). In areas that are frequently exposed to the sun, photoaging blends with the process of intrinsic aging, resulting in an increased senescent cells number and consequently accelerating the aging process. The severity of photodamage depends on constitutional factors, including skin phototype (skin color, tanning capacity), intensity, and duration of sunlight/UV exposure. Aging affects nearly every aspect of cutaneous biology, including pigmentation. Clinically, the phenotype of age pigmented skin has a mottled, uneven color, primarily due to age spots, with or without hypopigmentation. Uneven pigmentation might be attributed to the hyperactivation of melanocytes, altered distribution of pigment, and turnover. In addition to direct damage to pigment-producing cells, photodamage alters the physiological crosstalk between keratinocytes, fibroblasts, endothelial cells, and melanocytes responsible for natural pigmentation homeostasis. Interestingly, age-independent diffuse expression of senescence-associated markers in the dermal and epidermal compartment is also associated with vitiligo, suggesting that premature senescence plays an important role in the pathology.

Integrated analysis of miRNA-mRNA networks reveals a strong anti-skin cancer signature in vitiligo epidermis

Expression of microRNAs (miRNAs) is often dysregulated in several cancers, including non-melanoma skin cancer (NMSC). Individuals with vitiligo possess a deregulated miRnome along with a lower risk of developing NMSCs. We used data sets from our previously published studies on vitiligo epidermis to construct functional miRNA-mRNA networks to understand the molecular basis underlying the lower incidence of NMSC observed in individuals with vitiligo. miRTarBase database was used to fetch the experimentally validated targets of differentially expressed miRNAs and two protein-protein interaction (PPI) networks were constructed for the miRNA-mRNA interactions (230 downregulated targets of 5 upregulated miRNAs and 47 upregulated mRNAs targeted by 12 downregulated miRNAs). Pathway enrichment analysis identified RNA biogenesis and transport as well as cell adhesion to be perturbed in vitiligo. Further, oncogenic transcription factors (OTFs) that were upregulated in publicly available squamous cell carcinoma (SCC) or basal cell carcinoma (BCC) microarray data were compared with that of vitiligo to decode skin cancer-specific molecular signatures. We identified three significantly upregulated miRNAs, miR-31-5p, miR-31-3p and miR-194-3p in lesional epidermis that could negatively regulate seven oncogenic transcription factors, FOXC1, AR, SP1, YY1, GLI2, TP53 and RARA, known to be over-expressed in SCC or BCC. Taken together, our study identified a perturbed miRNA-regulated transcriptome, which potentially confers protection to vitiligo skin from an increased incidence of NMSC.

The Role of the NKG2D in Vitiligo

Vitiligo is an acquired multifactorial disease that affects melanocytes and results in skin depigmentation. In this review, we examine the role of cells stress and self-reactive T cells responses. Given the canonical and non-canonical functions of NKG2D, such as authenticating stressed target and enhance TCR signaling, we examine how melanocyte stress leads to the expression of ligands that are recognized by the activating receptor NKG2D, and how its signaling results in the turning of T cells against self (melanocyte suicide by proxy). We also discuss how this initiation phase is followed by T cell perpetuation, as NKG2D signaling results in self-sustained long-lasting T cells, with improved cytolytic properties.

Immunomodulatory and antimicrobial non-mulberry Antheraea mylitta silk fibroin accelerates in vitro fibroblast repair and regeneration by protecting oxidative stress

The antimicrobial nature of Antharaea mylitta silk-fibroin (SF) is reported but antioxidant potential and the immunomodulatory role towards the fibroblast cell repair process is not explored. Polyurethane is reported to have inflammatory potential by mononuclear cells directed cytokine release, which can guide fibroblast repair. Present study demonstrates the conjunctive effect of inflammatory PU/SF to regulate the favorable shift from pro-inflammatory to anti-inflammatory cytokine stimulation for accelerated fibroblast repair. Minimal inhibitory concentration of SF was determined against pathogenic strains and the effect of SF was investigated for fibroblast NIH3T3 cell adhesion. SF doses (8, 8.5, 9 mg mL⁻¹) were found to be greater than both the IC₅₀ of DPPH scavenging and the ED₅₀ for NIH3T3 proliferation. Anti-lipid peroxidase (ALP) activity of SF doses and citric acid-treated NIH3T3 cells were compared under hydrogen peroxide (H₂O₂) induced oxidative stress. 9 mg mL⁻¹ SF showed greater ALP activity than the citric acid standard. SF-driven protection to oxidative damage was measured by viable cell fraction in trypan blue dye exclusion assay where 9 mg mL⁻¹ SF showed the highest viability (p ≤ 0.05). 9 mg mL⁻¹ SF was blended with PU for scaffold (w/v = 2 : 5, 2 : 7, 2 : 9) fabrication. The protective effect of PU/SF (2 : 5, 2 : 7, 2 : 9) against oxidative stress was verified by damaged cell survival in MTT assay and DNA quantification. The highest number of cells survived on PU/SF (2 : 9) at all intervals (p ≤ 0.01) upon oxidative damage; PU/SF (2 : 9) was also fabricated by employing the immobilization technique. Immobilized PU/SF (2 : 9) exhibited a greater zone of microbial inhibition, a higher extent of inhibition to microbial adherence, and caused more LDH release from bacterial cell membrane due to membrane rupture, resulting in bacterial cell death (E. coli, K. pneumoniae, P. aeruginosa, S. aureus) compared to the experimental results shown by blended PU/SF (2 : 9). The protective nature of PU/SF (2 : 9) against oxidative stress was ensured through the LDH activity of damaged NIH3T3 cells. Initial raised IL-6, TNF-alpha (pro-inflammatory cytokines) and lowered IL-8, IL-10 (anti-inflammatory cytokine) profiles coupled with fallen IL-6, TNF-alpha, and elevated IL-8, IL-10 at later hours synergistically progress the inflammatory phase of in vitro scratch wound repair in mononuclear culture treated by PU/SF (2 : 9).

Initially SF accelerated pro-inflammatory cytokines, restricted anti-inflammatory cytokines; later it regulated in reverse order. SF potentially eradicated ROS and promoted Ki-67 cellular regeneration whereas pristine PU could not.

Skin pigmentation and its control: From ultraviolet radiation to stem cells

In the light of substantial discoveries in epithelial and hair pigmentation pathophysiology, this review summarizes the current understanding of skin pigmentation mechanisms. Melanocytes are pigment-producing cells, and their key regulating transcription factor is the melanocyte-specific microphthalmia-associated transcription factor (m-MITF). Ultraviolet (UV) radiation is a unique modulator of skin pigmentation influencing tanning pathways. The delayed tanning pathway occurs as UVB produces keratinocyte DNA damage, causing p53-mediated expression of the pro-opiomelanocortin (POMC) gene that is processed to release α-melanocyte-stimulating hormone (α-MSH). α-MSH stimulates the melanocortin 1 receptor (MC1R) on melanocytes, leading to m-MITF expression and melanogenesis. POMC cleavage also releases β-endorphin, which creates a neuroendocrine pathway that promotes UV-seeking behaviours. Mutations along the tanning pathway can affect pigmentation and increase the risk of skin malignancies. MC1R variants have received considerable attention, yet the allele is highly polymorphic with varied phenotypes. Vitiligo presents with depigmented skin lesions due to autoimmune destruction of melanocytes. UVB phototherapy stimulates melanocyte stem cells in the hair bulge to undergo differentiation and upwards migration resulting in perifollicular repigmentation of vitiliginous lesions, which is under sophisticated signalling control. Melanocyte stem cells, normally quiescent, undergo cyclic activation/differentiation and downward migration with the hair cycle, providing pigment to hair follicles. Physiological hair greying results from progressive loss of melanocyte stem cells and can be accelerated by acute stress-induced, sympathetic driven hyperproliferation of the melanocyte stem cells. Ultimately, by reviewing the pathways governing epithelial and follicular pigmentation, numerous areas of future research and potential points of intervention are highlighted.

An update on Vitiligo pathogenesis

Vitiligo, the most common depigmenting disorder of the skin, is undergoing a period of intense advances in both disease understanding and therapeutic possibilities leading the way to the beginning of a new era for the disorder. Its pathophysiology has gathered the attention of researchers for years, and many advances have been made in the clarification of the interaction between different factors that result in depigmented macule formation. The complex interplay between non-immunological and immunological factors in vitiligo is key for the development of the disease, and the participation of cells other than melanocytes, such as keratinocytes, fibroblasts, natural killer cells, and innate lymphoid cells, has been shown. Recent advances have also brought to the understanding of the complex part played by a specific subtype of T cells: T-resident memory cells. This review analyzes some of the most recent insights in vitiligo pathogenesis underlining the interactions between different cell types, which are the basis for the therapeutic approaches under development.

The enigma and challenges of vitiligo pathophysiology and treatment

Vitiligo is the most common acquired pigmentary disorder, which afflicts 0.5%-1% of the world population, and is characterized by depigmented skin patches resulting from melanocyte loss. Vitiligo has a complex etiology and varies in its manifestations, progression, and response to treatment. It presents as an autoimmune disease, evidenced by circulating melanocyte-specific antibodies, and association with other autoimmune diseases. However, autoimmunity may be secondary to the high oxidative stress in vitiligo skin and to intrinsic defects in melanocytes and their microenvironment, which contribute to aberrant stress response, neo-antigenicity, and susceptibility of melanocytes to immune attack and apoptosis. There is also a genetic predisposition to vitiligo, which sensitizes melanocytes to environmental agents, such as phenolic compounds. Currently, there are different treatment modalities for re-pigmenting vitiligo skin. However, when repigmentation is achieved, the major challenge is maintaining the pigmentation, which is lost in 40% of cases. In this review, we present an overview of the clinical aspects of vitiligo, its pathophysiology, the intrinsic defects in melanocytes and their microenvironment, and treatment strategies. Based on lessons from the biology of human melanocytes, we present our perspective of how repigmentation of vitiligo skin can be achieved and sustained.

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

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

Basal cell carcinoma: Epidemiology; pathophysiology; clinical and histological subtypes; and disease associations

As the most common human cancer worldwide and continuing to increase in incidence, basal cell carcinoma is associated with significant morbidity and cost. Continued advances in research have refined both our insight and approach to this seemingly ubiquitous disease. This 2-part continuing medical education article will provide a comprehensive and contemporary review of basal cell carcinoma. The first article in this series describes our current understanding of this disease regarding epidemiology, cost, clinical and histopathologic presentations, carcinogenesis, natural history, and disease associations.

Increased levels of mitochondrial DNA copy number in patients with vitiligo

BACKGROUND

Oxidative stress is known to be involved in the pathogenesis of autoimmune diseases such as vitiligo. Evidence suggests that the human mitochondrial DNA copy number (mtDNAcn) is vulnerable to damage mediated by oxidative stress. The purpose of this study was to examine and compare peripheral blood mtDNAcn and oxidative DNA damage byproducts (8-hydroxy-2-deoxyguanosine; 8-OHdG) in patients with vitiligo and healthy controls (HCs).

METHODS

The relative mtDNAcn and the oxidative damage (formation of 8-OHdG in mtDNA) of each sample were determined by real-time quantitative PCR. Blood samples were obtained from 56 patients with vitiligo and 46 HCs.

RESULTS

The mean mtDNAcn and the degree of mtDNA damage were higher in patients with vitiligo than in HCs.

CONCLUSION

These data suggest that increase in mtDNAcn and oxidative DNA damage may be involved in the pathogenesis of vitiligo.

No Association between Vitiligo and Obesity: A Case-Control Study

OBJECTIVE

The purpose of this study was to investigate the relationship between vitiligo and body mass index (BMI) to assess the possible association between vitiligo and obesity.

SUBJECTS AND METHODS

This was a case-control study on a total of 400 participants, i.e., 200 patients with vitiligo and 200 healthy volunteers. Medical assessments were performed by dermatologists using the modified Vitiligo European Task Force form. The height and weight of all of the participants were measured and used to calculate the BMI. Data were analyzed using multivariate logistic regression models. Adjustment for age and gender was carried out preliminarily in the case-control analysis, whereas a forward stepwise selection algorithm was used to assess which independent factors were associated with a BMI ≥30 or a BMI ≤18.5.

RESULTS

Comparison of the vitiligo and control groups revealed the absence of a significant association. The multivariate analysis of factors associated with a high BMI (≥30) in vitiligo patients showed a significant association between a high BMI and a sudden onset of vitiligo (p = 0.021; OR = 3.83; 95% CI 1.22-11.99) and the presence of inflammation and pruritus (p = 0.031; OR = 3.26; 95% CI 1.11-9.57). No significant association was observed in the analysis of factors associated with a low BMI (≤18.5) in vitiligo patients.

CONCLUSION

In this study, vitiligo did not appear to be associated with a high BMI; obesity might not be a risk factor for vitiligo, in contrast to most autoimmune diseases which are significantly associated with obesity.

Association of Leukotrichia in Vitiligo and Asp148Glu Polymorphism of Apurinic/Apyrimidinic Endonuclease 1

Background:

Oxidative stress and increased DNA damage have been implicated in the etiopathogenesis of vitiligo. Oxidative DNA damage is mainly repaired by the base excision repair (BER) pathway.

Aim:

We sought to determine whether polymorphisms in DNA repair genes may have a role in the pathogenesis of vitiligo.

Materials and Methods:

We conducted a study including 100 patients with vitiligo and age- and sex-matched 193 control subjects to examine the role of single-nucleotide polymorphisms of BER genes, human 8-oxoG DNA N-glycosylase 1 (codon 326), apurinic/apyrimidinic endonuclease 1 (APE1) (codon 148), and X-ray repair cross-complementing group 1 (codon 399) as risk factors for vitiligo. These polymorphisms were determined by quantitative real-time polymerase chain reaction and melting curve analysis.

Results:

No significant association was observed between the variant alleles of studied genes and vitiligo.

Conclusion:

However, we showed that the presence of APE1 148Glu variant allele is associated with leukotrichia. This preliminary study suggests that APE1 (codon 148) polymorphism may play a role in vitiligo pathogenesis.

Epidermal hydrogen peroxide is not increased in lesional and non-lesional skin of vitiligo

It is widely believed that the loss of the epidermal melanocytes in vitiligo is basically due to excessive oxidative stress. Previous research work described abnormal elevation of the absolute concentration of the epidermal hydrogen peroxide (H₂O₂) in lesional and non-lesional skin of vitiligo. Based on this finding, our primary research objective was to use this feature as a screening marker in individuals at a great risk of developing vitiligo. Ninety-six patients of non-segmental vitiligo (NSV) of varying durations, skin phototypes, and treatment modalities (psoralen UVA-, narrow band UVB-treated) were recruited for this study. Raman spectroscopic measurements, using an external probehead, of the lesional and non-lesional skin were obtained, and the resulting spectra were analyzed using the Opus software package of the MultiRam spectrometer and the intensity of the peak at 875 cm^-1 that represents the absolute concentration of H₂O₂ was calculated. Contrary to previous reports, in patients of skin phototype IV, the absolute concentrations of H₂O₂ in non-lesional and lesional NSV of all groups were non-significantly decreased compared to normal control. In patients of NSV of skin phototype V, the decrease in the absolute concentrations of H₂O₂ was not significant in the untreated group, and a slight non-significant increase in the NBUVB-treated group was noted. However, in the PUVA-treated group, the non-lesional skin demonstrated significant increase in the absolute concentration of H₂O₂, whereas the lesional skin showed only a slight non-significant increase compared to normal control. In NSV patients of skin phototype VI who were previously treated with PUVA, the non-lesional skin showed a slight non-significant increase in the absolute concentration of H₂O₂; however, the lesional skin showed a marked significant decrease compared to normal control and the non-lesional skin. Thereof, one can conclude that the epidermal H₂O₂ is not increased in NSV as previously thought and may not be responsible for the oxidative stress that leads to the melanocytes destruction, the hallmark of vitiligo pathogenesis.

The impact of skin colour on human photobiological responses

Terrestrial solar ultraviolet radiation (UVR) exerts both beneficial and adverse effects on human skin. Epidemiological studies show a lower incidence of skin cancer in people with pigmented skins compared to fair skins. This is attributed to photoprotection by epidermal melanin, as is the poorer vitamin D status of those with darker skins. We summarize a wide range of photobiological responses across different skin colours including DNA damage and immunosuppression. Some studies show the generally modest photoprotective properties of melanin, but others show little or no effect. DNA photodamage initiates non‐melanoma skin cancer and is reduced by a factor of about 3 in pigmented skin compared with white skin. This suggests that if such a modest reduction in DNA damage can result in the significantly lower skin cancer incidence in black skin, the use of sunscreen protection might be extremely beneficial for susceptible population. Many contradictory results may be explained by protocol differences, including differences in UVR spectra and exposure protocols. We recommend that skin type comparisons be done with solar‐simulated radiation and standard erythema doses or physical doses (J/m²) rather than those based solely on clinical endpoints such as minimal erythema dose (MED).

Stress chaperone mortalin regulates human melanogenesis

In order to identify the cellular factors involved in human melanogenesis, we carried out shRNA-mediated loss-of-function screening in conjunction with induction of melanogenesis by 1-oleoyl-2-acetyl-glycerol (OAG) in human melanoma cells using biochemical and visual assays. Gene targets of the shRNAs (that caused loss of OAG-induced melanogenesis) and their pathways, as determined by bioinformatics, revealed involvement of proteins that regulate cell stress response, mitochondrial functions, proliferation, and apoptosis. We demonstrate, for the first time, that the mitochondrial stress chaperone mortalin is crucial for melanogenesis. Upregulation of mortalin was closely associated with melanogenesis in in vitro cell-based assays and clinical samples of keloids with hyperpigmentation. Furthermore, its knockdown resulted in compromised melanogenesis. The data proposed mortalin as an important protein that may be targeted to manipulate pigmentation for cosmetic and related disease therapeutics.

Vitiligo: How do oxidative stress-induced autoantigens trigger autoimmunity?

Vitiligo is a common depigmentation disorder characterized by a loss of functional melanocytes and melanin from epidermis, in which the autoantigens and subsequent autoimmunity caused by oxidative stress play significant roles according to hypotheses. Various factors lead to reactive oxygen species (ROS) overproduction in the melanocytes of vitiligo: the exogenous and endogenous stimuli that cause ROS production, low levels of enzymatic and non-enzymatic antioxidants, disturbed antioxidant pathways and polymorphisms of ROS-associated genes. These factors synergistically contribute to the accumulation of ROS in melanocytes, finally leading to melanocyte damage and the production of autoantigens through the following ways: apoptosis, accumulation of misfolded peptides and cytokines induced by endoplasmic reticulum stress as well as the sustained unfolded protein response, and an 'eat me' signal for phagocytic cells triggered by calreticulin. Subsequently, autoantigens presentation and dendritic cells maturation occurred mediated by the release of antigen-containing exosomes, adenosine triphosphate and melanosomal autophagy. With the involvement of inducible heat shock protein 70, cellular immunity targeting autoantigens takes the essential place in the destruction of melanocytes, which eventually results in vitiligo. Several treatments, such as narrow band ultraviolet, quercetin and α-melanophore-stimulating hormone, are reported to be able to lower ROS thereby achieving repigmentation in vitiligo. In therapies targeting autoimmunity, restore of regulatory T cells is absorbing attention, in which narrow band ultraviolet also plays a role.

Vitiligo

Vitiligo is an acquired depigmenting disorder that affects 0.5% to 2% of the world population. Three different forms are classified according to the distribution of lesions; namely non-segmental, segmental and mixed vitiligo. Vitiligo is associated with polymorphisms in genes involved in the immune response and in melanogenesis. However, environmental factors are required for the development of manifest disease. In general, the diagnosis is clinical and no laboratory tests or biopsies are required. Metabolic alterations are central to current concepts in pathophysiology. They induce an increased generation of reactive oxygen species and susceptibility to mild exogenous stimuli in the epidermis. This produces a senescent phenotype of skin cells, leads to the release of innate immune molecules, which trigger autoimmunity, and ultimately causes dysfunction and death of melanocytes. Clinical management aims to halt depigmentation, and to either repigment or depigment the skin, depending on the extent of disease. New therapeutic approaches include stimulation of melanocyte differentiation and proliferation through α-melanocyte-stimulating hormone analogues and through epidermal stem cell engineering. Several questions remain unsolved, including the connection between melanocyte depletion and stem cell exhaustion, the underlying degenerative mechanisms and the biological mediators of cell death. Overall, vitiligo is an excellent model for studying degenerative and autoimmune processes and for testing novel approaches in regenerative medicine. For an illustrated summary of this Primer, visit: http://go.nature.com/vIhFSC.

Rapid fluorescence spectroscopic characterization of salivary DNA of normal subjects and OSCC patients using ethidium bromide

Recently, deoxyribonucleic acid (DNA) based biomarker(s) detection has been employed for cancer diagnosis. Earlier reports have suggested the presence of more DNA in the saliva of oral squamous cell carcinoma (OSCC) than normal by electrophoresis technique. Based on these, steady state and excited state kinetics of salivary DNA has been performed with 27 normal subjects and 67 OSCC patients saliva using ethidium bromide as a probe to look for the possibility in discrimination between them. On statistical analysis the sensitivity and specificity of 88.9 and 94.0 % has been achieved from the fluorescence emission spectra and 88.9 and 92.5 % with that of fluorescence excitation.

Palladium and platinum nanoparticles attenuate aging-like skin atrophy via antioxidant activity in mice

Cu-Zn superoxide dismutase (Sod1) loss causes a redox imbalance as it leads to excess superoxide generation, which results in the appearance of various aging-related phenotypes, including skin atrophy. Noble metal nanoparticles, such as palladium (Pd) and platinum (Pt) nanoparticles, are considered to function as antioxidants due to their strong catalytic activity. In Japan, a mixture of Pd and Pt nanoparticles called PAPLAL has been used to treat chronic diseases over the past 60 years. In the present study, we investigated the protective effects of PAPLAL against aging-related skin pathologies in mice. Transdermal PAPLAL treatment reversed skin thinning associated with increased lipid peroxidation in Sod1^−/− mice. Furthermore, PAPLAL normalized the gene expression levels of Col1a1, Mmp2, Has2, Tnf-α, Il-6, and p53 in the skin of the Sod1^−/− mice. Pt nanoparticles exhibited marked SOD and catalase activity, while Pd nanoparticles only displayed weak SOD and catalase activity in vitro. Although the SOD and catalase activity of the Pt nanoparticles significantly declined after they had been oxidized in air, a mixture of Pd and Pt nanoparticles continued to exhibit SOD and catalase activity after oxidation. Importantly, a mixture of Pd and Pt nanoparticles with a molar ratio of 3 or 4 to 1 continued to exhibit SOD and catalase activity after oxidation, indicating that Pd nanoparticles prevent the oxidative deterioration of Pt nanoparticles. These findings indicate that PAPLAL stably suppresses intrinsic superoxide generation both in vivo and in vitro via SOD and catalase activity. PAPLAL is a potentially powerful tool for the treatment of aging-related skin diseases caused by oxidative damage.

Melanocytes as instigators and victims of oxidative stress

Epidermal melanocytes are particularly vulnerable to oxidative stress owing to the pro-oxidant state generated during melanin synthesis, and to the intrinsic antioxidant defenses that are compromised in pathologic conditions. Melanoma is thought to be oxidative stress driven, and melanocyte death in vitiligo is thought to be instigated by a highly pro-oxidant state in the epidermis. We review the current knowledge about melanin and the redox state of melanocytes, how paracrine factors help counteract oxidative stress, the role of oxidative stress in melanoma initiation and progression and in melanocyte death in vitiligo, and how this knowledge can be harnessed for melanoma and vitiligo treatment.

FoxP3 expression in papillary thyroid carcinoma: a possible resistance biomarker to iodine 131 treatment

BACKGROUND

The forkhead transcription factor FoxP3 plays an important role in regulatory T cell (Treg) functions. Tregs are critical in maintaining immunologic tolerance. It has been shown that vaccination against FoxP3-expressing cells is associated with enhancement of tumor immunity. Tregs appear to be increased in blood and in the tumor microenvironment of patients with different cancer types. Tumor cells themselves can express FoxP3. The present study investigates the possible role of FoxP3 expression in a series of human papillary thyroid cancers with a mean follow-up time of 15 years.

METHODS

One hundred five cases of papillary thyroid carcinoma (PTC) were investigated, and FoxP3 expression was evaluated in both tumor cells and tumor-associated infiltrates. For all patients, clinical/pathologic features were considered and the results analyzed by statistical tests.

RESULTS

Of the 105 PTC cases, 45 (43%) scored FoxP3-positive and 60 (57%) were negative. FoxP3 staining was localized predominantly in the cytoplasm of tumor cells. In some cases, both nuclear and cytoplasmic staining was seen in infiltrating cells. FoxP3 expression in tumor cells was correlated with the presence of extrathyroid invasion (p=0.04) and distant metastasis (p=0.04), but not with overall survival. Interestingly, FoxP3 expression in neoplastic cells was significantly associated with a resistance phenotype to radioiodine treatment (p=0.041).

CONCLUSIONS

The data show an association of FoxP3 expression with features of PTC that seem to have a specific impact on radioiodine sensitivity.

Basic evidence for epidermal H2O2/ONOO(-)-mediated oxidation/nitration in segmental vitiligo is supported by repigmentation of skin and eyelashes after reduction of epidermal H2O2 with topical NB-UVB-activated pseudocatalase PC-KUS

Nonsegmental vitiligo (NSV) is characterized by loss of inherited skin color. The cause of the disease is still unknown despite accumulating in vivo and in vitro evidence of massive epidermal oxidative stress via H2O2 and peroxynitrite (ONOO(-)) in affected individuals. The most favored hypothesis is based on autoimmune mechanisms. Strictly segmental vitiligo (SSV) with dermatomal distribution is a rare entity, often associated with stable outcome. Recently, it was documented that this form can be associated with NSV (mixed vitiligo). We here asked the question whether ROS and possibly ONOO(-) could be players in the pathogenesis of SSV. Our in situ results demonstrate for the first time epidermal biopterin accumulation together with significantly decreased epidermal catalase, thioredoxin/thioreoxin reductase, and MSRA/MSRB expression. Moreover, we show epidermal ONOO(-) accumulation. In vivo FT-Raman spectroscopy reveals the presence of H2O2, methionine sulfoxide, and tryptophan metabolites; i.e., N-formylkynurenine and kynurenine, implying Fenton chemistry in the cascade (n=10). Validation of the basic data stems from successful repigmentation of skin and eyelashes in affected individuals, regardless of SSV or segmental vitiligo in association with NSV after reduction of epidermal H2O2 (n=5). Taken together, our contribution strongly supports H2O2/ONOO-mediated stress in the pathogenesis of SSV. Our findings offer new treatment intervention for lost skin and hair color.

Genetic variants of the APE1 gene and the risk of vitiligo in a Chinese population: a genotype-phenotype correlation study

Vitiligo is an acquired depigmentation disorder, and reactive oxygen species play an important role in melanocyte damage. Base excision repair is the major pathway responsible for removing reactive oxygen species-induced DNA damage, in which APE1, ADPRT, and XRCC1 play key roles. To investigate the association between genetic variations of these genes and the risk of vitiligo in Chinese populations, we genotyped APE1-Asp148Glu, ADPRT-Val762Ala, and XRCC1-Arg399Gln polymorphisms and measured serum 8-OHdG levels in a hospital-based case-control study. We found that a significantly increased risk of vitiligo was associated with the APE1 Asp/Glu (adjusted odds ratio (OR) 1.24; 95% confidence interval (CI) 1.02-1.52) and Glu/Glu genotypes (adjusted OR 1.48; 95% CI 1.13-1.93), compared with the APE1 Asp/Asp genotype, whereas no vitiligo risk was associated with the genotypes ADPRT-Val762Ala and XRCC1-Arg399Gln. Furthermore, serum 8-OHdG levels were elevated in the APE1-148Glu allele carriers (Asp/Glu+Glu/Glu), in an allele dose-response manner, with the risk of vitiligo (Ptrend<0.05). In addition, we found that the APE1-148Glu variant increased the 8-OHdG levels of cultured human melanocytes treated with H2O2, without any impact on the endonuclease activity. These data suggest that the APE1-Asp148Glu polymorphism aggravates oxidative stress in human melanocytes and contributes to genetic predisposition to vitiligo in Chinese people.

Evaluation of total oxidant and antioxidant status in localized and generalized vitiligo

BACKGROUND

Vitiligo is an acquired depigmentation disorder, and oxidative stress is suggested to have a major role in its aetiopathogenesis.

AIM

To assess whether oxidative stress has a greater role in generalized than in localized vitiligo.

METHODS

We assessed 31 patients with active vitiligo (17 localized, 14 generalized) and 38 healthy controls. Serum total oxidant status (TOS), total antioxidant status (TAS) and oxidative stress index (OSI) were determined.

RESULTS

Patients with vitiligo had significantly lower TAS and higher TOS and OSI values than controls. Both localized and generalized vitiligo were associated with lower TAS and higher TOS and OSI values, compared with controls, and all three did not differ with vitiligo type.

CONCLUSIONS

A systemic oxidative stress exists in patients with vitiligo. These results indicate that the global antioxidant capacity of patients might have been exhausted through a defence mechanism against oxidative processes. The imbalance in TOS/TAS status may have an important role in the aetiopathogenesis of vitiligo, regardless of the clinical variant of the disease.

Vitiligo: interplay between oxidative stress and immune system

Vitiligo is a multifactorial polygenic disorder with a complex pathogenesis, linked with both genetic and non-genetic factors. The precise modus operandi for vitiligo pathogenesis has remained elusive. Theories regarding loss of melanocytes are based on autoimmune, cytotoxic, oxidant-antioxidant and neural mechanisms. Reactive oxygen species (ROS) in excess have been documented in active vitiligo skin. Numerous proteins in addition to tyrosinase are affected. It is possible that oxidative stress is one among the main principal causes of vitiligo. However, there also exists ample evidence for altered immunological processes in vitiligo, particularly in chronic and progressive conditions. Both innate and adaptive arms of the immune system appear to be involved as a primary event or as a secondary promotive consequence. There is speculation on the interplay, if any, between ROS and the immune system in the pathogenesis of vitiligo. The article focuses on the scientific evidences linking oxidative stress and immune system to vitiligo pathogenesis giving credence to a convergent terminal pathway of oxidative stress-autoimmunity-mediated melanocyte loss.

Vitiligo: a possible model of degenerative diseases

Vitiligo is characterized by the progressive disappearance of pigment cells from skin and hair follicle. Several in vitro and in vivo studies show evidence of an altered redox status, suggesting that loss of cellular redox equilibrium might be the pathogenic mechanism in vitiligo. However, despite the numerous data supporting a pathogenic role of oxidative stress, there is still no consensus explanation underlying the oxidative stress-driven disappear of melanocytes from the epidermis. In this study, in vitro characterization of melanocytes cultures from non-lesional vitiligo skin revealed at the cellular level aberrant function of signal transduction pathways common with neurodegenerative diseases including modification of lipid metabolism, hyperactivation of mitogen-activated protein kinase (MAPK) and cAMP response element-binding protein (CREB), constitutive p53-dependent stress signal transduction cascades, and enhanced sensibility to pro-apoptotic stimuli. Notably, these long-term effects of subcytotoxic oxidative stress are also biomarkers of pre-senescent cellular phenotype. Consistent with this, vitiligo cells showed a significant increase in p16 that did not correlate with the chronological age of the donor. Moreover, vitiligo melanocytes produced many biologically active proteins among the senescence-associated secretory phenotype (SAPS), such as interleukin-6 (IL-6), matrix metallo proteinase-3 (MMP3), cyclooxygenase-2 (Cox-2), insulin-like growth factor-binding protein-3 and 7 (IGFBP3, IGFBP7). Together, these data argue for a complicated pathophysiologic puzzle underlying melanocytes degeneration resembling, from the biological point of view, neurodegenerative diseases. Our results suggest new possible targets for intervention that in combination with current therapies could correct melanocytes intrinsic defects.

Blunted epidermal L-tryptophan metabolism in vitiligo affects immune response and ROS scavenging by Fenton chemistry, part 2: Epidermal H2O2/ONOO(-)-mediated stress in vitiligo hampers indoleamine 2,3-dioxygenase and aryl hydrocarbon receptor-mediated immune response signaling

Vitiligo is characterized by a mostly progressive loss of the inherited skin color. The cause of the disease is still unknown, despite accumulating in vivo and in vitro evidence of massive oxidative stress via hydrogen peroxide (H(2)O(2)) and peroxynitrite (ONOO(-)) in the skin of affected individuals. The most favored hypothesis is based on autoimmune mechanisms. Since depletion of the essential amino acid L-tryptophan (Trp) severely affects various immune responses, we here looked at Trp metabolism and signaling in these patients. Our in vivo and in vitro data revealed total absence of epidermal Trp hydroxylase activities and the presence of H(2)O(2)/ONOO(-) deactivated indoleamine 2,3-dioxygenase. Aryl hydrocarbon receptor signaling is severely impaired despite the ligand (Trp dimer) being formed, as shown by mass spectrometry. Loss of this signal is supported by the absence of downstream signals (COX-2 and CYP1A1) as well as regulatory T-lymphocytes and by computer modeling. In vivo Fourier transform Raman spectroscopy confirmed the presence of Trp metabolites together with H(2)O(2) supporting deprivation of the epidermal Trp pool by Fenton chemistry. Taken together, our data support a long-expressed role for in loco redox balance and a distinct immune response. These insights could open novel treatment strategies for this disease.

Blunted epidermal L-tryptophan metabolism in vitiligo affects immune response and ROS scavenging by Fenton chemistry, part 1: Epidermal H2O2/ONOO(-)-mediated stress abrogates tryptophan hydroxylase and dopa decarboxylase activities, leading to low serotonin and melatonin levels

Vitiligo is characterized by a progressive loss of inherited skin color. The cause of the disease is still unknown. To date, there is accumulating in vivo and in vitro evidence for massive oxidative stress via hydrogen peroxide (H(2)O(2)) and peroxynitrite (ONOO(-)) in the skin of affected individuals. Autoimmune etiology is the favored theory. Since depletion of the essential amino acid L-tryptophan (Trp) affects immune response mechanisms, we here looked at epidermal Trp metabolism via tryptophan hydroxylase (TPH) with its downstream cascade, including serotonin and melatonin. Our in situ immunofluorescence and Western blot data reveal significantly lower TPH1 expression in patients with vitiligo. Expression is also low in melanocytes and keratinocytes under in vitro conditions. Although in vivo Fourier transform-Raman spectroscopy proves the presence of 5-hydroxytryptophan, epidermal TPH activity is completely absent. Regulation of TPH via microphthalmia-associated transcription factor and L-type calcium channels is severely affected. Moreover, dopa decarboxylase (DDC) expression is significantly lower, in association with decreased serotonin and melatonin levels. Computer simulation supports H(2)O(2)/ONOO(-)-mediated oxidation/nitration of TPH1 and DDC, affecting, in turn, enzyme functionality. Taken together, our data point to depletion of epidermal Trp by Fenton chemistry and exclude melatonin as a relevant contributor to epidermal redox balance and immune response in vitiligo.

Neuro-Immuno-Endocrine Processes in Vitiligo Pathogenesis

Vitiligo is a cutaneous disorder of depigmentation, clinically characterized by well-demarcated, white macules of varying size and distribution. It can affect up to 2% of the population, especially younger ages. In spite of recent findings implicating genetic, immune and oxidative stress factors, the exact pathogenesis of vitiligo remains obscure. Here, we briefly discuss the prevailing theories, and offer new suggestions that could explain in part the damage of melanocyte in the vitiliginous lesions. Our emerging hypothesis is that neuropeptides released from peripheral nerve endings could synergize with new cytokines to adversely affect melanocyte function and viability. These may include corticotropin-releasing hormone (CRH) and neurotensin (NT), as well as interleukin 33 (IL-33) and thymic stromal lymphopoietin (TSLP). Such interactions could serve the basis for further research, possibly leading to new treatments.

Role of fibroblast-derived growth factors in regulating hyperpigmentation of solar lentigo

BACKGROUND

Cutaneous pigmentation is regulated by a complex melanogenic network in which both keratinocytes and fibroblasts synthesize growth factors and cytokines. Solar lentigo (SL) is characterized by hyperpigmented lesions occurring on photodamaged skin areas. Despite the association of SL to ultraviolet (UV) exposure, the mechanisms underlying the development of these spots are not completely defined.

OBJECTIVES

To analyse the involvement of the fibroblast-derived growth factors, hepatocyte growth factor (HGF), keratinocyte growth factor (KGF) and stem cell factor (SCF) in SL hyperpigmentation; to evaluate whether the photoageing process occurring in fibroblasts could be responsible for the altered expression of these cytokines; and to investigate a new possible role of KGF in regulating pigmentation through the specific induction of melanogenic cytokines by keratinocytes.

METHODS

We performed immunohistochemical analysis of HGF, KGF and SCF on SL biopsies. We analysed the mRNA expression of these cytokines using an in vitro model of photoageing induced on fibroblasts. Finally, we evaluated the effects of KGF on the expression of melanogenic cytokines at the mRNA and protein levels on keratinocytes.

RESULTS

We found positive staining for HGF, KGF and SCF in the upper dermis of SL lesions and a significant induction of the three cytokines in photoaged fibroblasts. We also demonstrated the contribution of KGF to pigmentation, showing its ability specifically to modulate the expression of SCF in keratinocytes.

CONCLUSIONS

Fibroblasts may be persistently activated by UV exposure to release melanogenic growth factors; this inducible cytokine network acts both directly and indirectly through keratinocytes and may contribute to the hyperpigmentation of SL.