Oxidative stress via hydrogen peroxide affects proopiomelanocortin peptides directly in the epidermis of patients with vitiligo

Mitochondria-Melanocyte cellular interactions: An emerging mechanism of vitiligo pathogenesis

Mitochondria has emerged as a potential modulator of melanocyte function other than just meeting its cellular ATP demands. Mitochondrial DNA defects are now an established cause of maternal inheritance diseases. Recent cellular studies have highlighted the mitochondrial interaction with other cellular organelles that lead to disease conditions such as in Duchenne muscular dystrophy, where defective mitochondria was found in melanocytes of these patients. Vitiligo, a depigmentory ailment of the skin, is another such disorder whose pathogenesis is now found to be associated with mitochondria. The complete absence of melanocytes at the lesioned site in vitiligo is a fact; however, the precise mechanism of this destruction is still undefined. In this review we have tried to discuss and link the emerging facts of mitochondrial function or its inter- and intra-organellar communications in vitiligo pathogenesis. Mitochondrial close association with melanosomes, molecular involvement in melanocyte-keratinocyte communication and melanocyte survival are new paradigm of melanogenesis that could ultimately account for vitiligo. This definitely adds the new dimensions to our understanding of vitiligo, its management and designing of future mitochondrial targeted therapy for vitiligo.

Enhanced Natural Strength: Lamiaceae Essential Oils and Nanotechnology in In Vitro and In Vivo Medical Research

The Lamiaceae is one of the most important families in the production of essential oils known to have a wide spectrum of biological activity. Recent research has highlighted the dermatological capabilities of various Lamiaceae essential oils, which appear to offer potential in free radical scavenging and anti-inflammatory activity. Some have also been extensively studied for their tissue remodeling and wound-healing, anti-aging, anti-melanogenic, and anti-cancer properties. Certain Lamiaceae essential oils are promising as novel therapeutic alternatives for skin disorders. This potential has seen substantial efforts dedicated to the development of modern formulations based on nanotechnology, enabling the topical application of various Lamiaceae essential oils. This review provides a comprehensive summary of the utilization of various essential oils from the Lamiaceae family over the past decade. It offers an overview of the current state of knowledge concerning the use of these oils as antioxidants, anti-inflammatory agents, wound-healers, anti-aging agents, anti-melanogenic agents, and anticancer agents, both alone and in combination with nanoparticles. Additionally, the review explores their potential applicability in patents regarding skin diseases.

Tetrahydrobiopterin as a Trigger for Vitiligo: Phototransformation during UV Irradiation

Vitiligo is a type of hypomelanosis. Tetrahydrobiopterin (H4Bip), the coenzyme of the initial stage of melanogenesis, appears to be a trigger for vitiligo. H4Bip is present in vitiligo in 3-5-fold excess and causes oxidative stress by triggering an autocatalytic cycle of excess hydrogen peroxide synthesis. Using quantum-chemical calculations, we have evaluated the possibility of H4Bip reactions occurring in the dark and under ultraviolet (UV) irradiation, including the formation of dihydropterin dimers. In order to simulate the oxidative stress, oxidative modification of human serum albumin (HSA) has been carried out in the presence of excessive H4Bip using the fluorescence method. The fraction of oxidized protein (FOP) has been calculated. It has been established that there is a strong oxidative modification of amino acids chromophores (tryptophan and tyrosine) in the protein (FOP 0.64). Under UV irradiation of the system (HSA + H4Bip), FOP is reduced to 0.39. Apparently, a part of H4Bip transforms into dihydropterin dimers and does not participate in the oxidative modification of the protein. The data on oxidative modification of HSA are consistent with dynamic light scattering: H4Bip promotes HSA aggregation with the formation of particles with a hydrodynamic radius Rh ≥ 2000 nm, which can become immunogenic.

Biochemical and molecular responses of Rosa damascena mill. cv. Kashan to salicylic acid under salinity stress

BACKGROUND

Today, salinity stress is one of the most important abiotic stresses in the world, because it causes damage to many agricultural products and reduces their yields. Oxidative stress causes tissue damages in plants, which occurs with the production of reactive oxygen species (ROS) when plants are exposed to environmental stresses such as salinity. Today, it is recommended to use compounds that increase the resistance of plants to environmental stresses and improve plant metabolic activities. Salicylic acid (SA), as an intracellular and extracellular regulator of the plant response, is known as one of these effective compounds. Damask rose (Rosa damascena Mill.) is a medicinal plant from the Rosaceae, and its essential oils and aromatic compounds are used widely in the cosmetic and food industries in the world. Therefore, considering the importance of this plant from both medicinal and ornamental aspects, for the first time, we investigated one of the native cultivars of Iran (Kashan). Since one of the most important problems in Damask rose cultivation is the occurrence of salinity stress, for the first time, we investigated the interaction of several levels of NaCl salinity (0, 4, 8, and 12 ds m^- 1) with SA (0, 0.5, 1, and 2 mM) as a stress reducer.

RESULTS

Since salinity stress reduces plant growth and yield, in this experiment, the results showed that the increase in NaCl concentration caused a gradual decrease in photosynthetic and morphological parameters and an increase in ion leakage. Also, increasing the level of salinity stress up to 12 ds m^- 1 affected the amount of chlorophyll, root length and leaf total area, all of which reduced significantly compared to plants under no stress. However, many studies have highlighted the application of compounds that reduce the negative effects of stress and increase plant resistance and tolerance against stresses. In this study, the application of SA even at low concentration (0.5 mM) could neutralize the negative effects of salinity stress in the Rosa damascena. In this regard, the results showed that salinity increases the activity of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD) and the concentration of proline, protein and glycine betaine (GB). Overexpression of antioxidant genes (Ascorbate Peroxidase (APX), CAT, Peroxidase (POD), Fe-SOD and Cu-SOD) showed an important role in salt tolerance in Damascus rose. In addition, 0.5 mm SA increased the activity of enzymatic and non-enzymatic systems and increased salinity tolerance.

CONCLUSIONS

The change in weather conditions due to global warming and increased dryness contributes to the salinization of the earth's surface soils. Therefore, it is of particular importance to measure the threshold of tolerance of roses to salinity stress and the effect of stress-reducing substances in plants. In this context, SA has various roles such as increasing the content of pigments, preventing ethylene biosynthesis, increasing growth, and activating genes involved in stress, which modifies the negative effects of salinity stress. Also, according to the results of this research, even in the concentration of low values, positive results can be obtained from SA, so it can be recommended as a relatively cheap and available material to improve production in saline lands.

Recognition of Melanocytes in Immuno-Neuroendocrinology and Circadian Rhythms: Beyond the Conventional Melanin Synthesis

Melanocytes produce melanin to protect the skin from UV-B radiation. Notwithstanding, the spectrum of their functions extends far beyond their well-known role as melanin production factories. Melanocytes have been considered as sensory and computational cells. The neurotransmitters, neuropeptides, and other hormones produced by melanocytes make them part of the skin’s well-orchestrated and complex neuroendocrine network, counteracting environmental stressors. Melanocytes can also actively mediate the epidermal immune response. Melanocytes are equipped with ectopic sensory systems similar to the eye and nose and can sense light and odor. The ubiquitous inner circadian rhythm controls the body’s basic physiological processes. Light not only affects skin photoaging, but also regulates inner circadian rhythms and communicates with the local neuroendocrine system. Do melanocytes “see” light and play a unique role in photoentrainment of the local circadian clock system? Why, then, are melanocytes responsible for so many mysterious functions? Do these complex functional devices work to maintain homeostasis locally and throughout the body? In addition, melanocytes have also been shown to be localized in internal sites such as the inner ear, brain, and heart, locations not stimulated by sunlight. Thus, what can the observation of extracutaneous melanocytes tell us about the “secret identity” of melanocytes? While the answers to some of these intriguing questions remain to be discovered, here we summarize and weave a thread around available data to explore the established and potential roles of melanocytes in the biological communication of skin and systemic homeostasis, and elaborate on important open issues and propose ways forward.

The Role of Oxidative Stress in the Pathogenesis of Vitiligo: A Culprit for Melanocyte Death

Vitiligo is a common chronic acquired pigmentation disorder characterized by loss of pigmentation. Among various hypotheses proposed for the pathogenesis of vitiligo, oxidative stress-induced immune response that ultimately leads to melanocyte death remains most widely accepted. Oxidative stress which causes elevated levels of reactive oxygen species (ROS) can lead to dysfunction of molecules and organelles, triggering further immune response, and ultimately melanocyte death. In recent years, a variety of cell death modes have been studied, including apoptosis, autophagy and autophagic cell death, ferroptosis, and other novel modes of death, which will be discussed in this review in detail. Oxidative stress is also strongly linked to these modes of death. Under oxidative stress, ROS could induce autophagy by activating the Nrf2 antioxidant pathway of melanocytes. However, persistent stimulation of ROS might eventually lead to excessive activation of Nrf2 antioxidant pathway, which in turn will inactivate autophagy. Moreover, ferroptosis may be triggered by oxidative-related transcriptional production, including ARE, the positive feedback loop related to p62, and the reduced activity and expression of GPX4. Therefore, it is reasonable to infer that these modes of death are involved in the oxidative stress response, and that oxidative stress also acts as an initiator for various modes of death through some complex mechanisms. In this study, we aim to summarize the role of oxidative stress in vitiligo and discuss the corresponding mechanisms of interaction between various modes of cell death and oxidative stress. These findings may provide new ideas for exploring the pathogenesis and potential therapeutic targets of vitiligo.

Current evidence to support the therapeutic potential of flavonoids in oxidative stress-related dermatoses

BACKGROUND

Skin, as a crucial external defense organ, is more vulnerable to oxidative stress (OS) insult, reactive oxygen species (ROS)-mediated OS in particular. OS results from a redox imbalance caused by various extrinsic stimuli and occurs once the oxidants production overwhelming the antioxidants capacity, through mediating in DNA damage, lipid peroxidation (LPO), protein oxidation and a serial of signaling pathways activation/inactivation, thereby offering favorable conditions for the occurrence and development of numerous diseases especially some dermatoses, e.g. psoriasis, vitiligo, skin photodamage, skin cancer, systemic sclerosis (SSc), chloasma, atopic dermatitis (AD), pemphigus, etc. Targeting OS molecular mechanism, a variety of anti-OS agents emerge, in which flavonoids, natural plant extracts, stand out.

OBJECTIVES

To discuss the possible mechanisms of OS mediating in dermatoses and summarize the properties of flavonoids as well as their applications in OS-related skin disorders.

METHODS

Published papers on flavonoids and OS-related skin diseases were collected and reviewed via database searching on PubMed, MEDLINE and Embase, etc.

RESULTS

It has been confirmed that flavonoids, belonging to polyphenols, are a class of plant secondary metabolites widely distributed in various plants and possess diverse bioactivities especially their potent antioxidant capacity. Moreover, flavonoids benefit to suppress OS via eliminating free radicals and mediating the corresponding signals, further excellently working in the prevention and management of OS-related skin diseases.

CONCLUSION

Flavonoids have the potential therapeutic effects on oxidative stress-related dermatoses. However, more studies on specific mechanism as well as the dosage of flavonoids are needed in future.

Anti-Melanogenic Mechanism of Tetrahydrocurcumin and Enhancing Its Topical Delivery Efficacy Using a Lecithin-Based Nanoemulsion

Tetrahydrocurcumin (THC) has been well known for its superior antioxidant properties. Therefore, it is speculated that it might be effective to relieve oxidative stress-induced diseases, such as skin hyperpigmentation. In this work, an in vitro B16F10 melanoma cell model was used to study the impact of THC on the melanogenic process under stressed conditions. It was demonstrated that THC could effectively inhibit the α-MSH (melanocyte-stimulating hormone) induced melanin production in B16F10 melanoma cells and the expressions of three key enzymes involved with the biosynthetic process of melanin, tyrosinase (TYR), tyrosinase-related protein 1 (TRP-1), and tyrosinase-related protein 2 (TRP-2), were all significantly reduced. In addition, an in vitro human keratinocyte cell model was used to investigate the potential protective role of THC on H₂O₂-induced cytotoxicity. It was found that THC could prevent H₂O₂-induced oxidative stress based on the results of both the cell viability study and the intracellular ROS (reactive oxygen species) study assessed by the flow cytometry. Last, THC was formulated into a lecithin based nanoemulsion, and an in vitro Franz diffusion cell study using Strat-M^® membrane concluded that the nanoemulsion could significantly enhance the membrane permeation compared to the unformatted THC suspension. This research demonstrated the anti-melanogenic benefits of THC on the melanoma and keratinocyte cell models and the topical delivery efficacy could be significantly enhanced using a lecithin based nanoemulsion.

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.

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.

Translational Neuroendocrinology of Human Skin: Concepts and Perspectives

Human skin responds to numerous neurohormones, neuropeptides, and neurotransmitters that reach it via the vasculature or skin nerves, and/or are generated intracutaneously, thus acting in a para- and autocrine manner. This review focuses on how neurohormones impact on human skin physiology and pathology. We highlight basic concepts, major open questions, and translational research perspectives in cutaneous neuroendocrinology and argue that greater emphasis on neuroendocrine human skin research will foster the development of novel dermatological therapies. Furthermore, human skin and its appendages can be used as highly accessible and clinically relevant model systems for probing nonclassical, ancestral neurohormone functions. This calls for close interdisciplinary collaboration between dermatologists, skin biologists, neuroendocrinologists, and neuropharmacologists.

The biology of human hair greying

Hair greying (canities) is one of the earliest, most visible ageing-associated phenomena, whose modulation by genetic, psychoemotional, oxidative, senescence-associated, metabolic and nutritional factors has long attracted skin biologists, dermatologists, and industry. Greying is of profound psychological and commercial relevance in increasingly ageing populations. In addition, the onset and perpetuation of defective melanin production in the human anagen hair follicle pigmentary unit (HFPU) provides a superb model for interrogating the molecular mechanisms of ageing in a complex human mini-organ, and greying-associated defects in bulge melanocyte stem cells (MSCs) represent an intriguing system of neural crest-derived stem cell senescence. Here, we emphasize that human greying invariably begins with the gradual decline in melanogenesis, including reduced tyrosinase activity, defective melanosome transfer and apoptosis of HFPU melanocytes, and is thus a primary event of the anagen hair bulb, not the bulge. Eventually, the bulge MSC pool becomes depleted as well, at which stage greying becomes largely irreversible. There is still no universally accepted model of human hair greying, and the extent of genetic contributions to greying remains unclear. However, oxidative damage likely is a crucial driver of greying via its disruption of HFPU melanocyte survival, MSC maintenance, and of the enzymatic apparatus of melanogenesis itself. While neuroendocrine factors [e.g. alpha melanocyte-stimulating hormone (α-MSH), adrenocorticotropic hormone (ACTH), ß-endorphin, corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH)], and micropthalmia-associated transcription factor (MITF) are well-known regulators of human hair follicle melanocytes and melanogenesis, how exactly these and other factors [e.g. thyroid hormones, hepatocyte growth factor (HGF), P-cadherin, peripheral clock activity] modulate greying requires more detailed study. Other important open questions include how HFPU melanocytes age intrinsically, how psychoemotional stress impacts this process, and how current insights into the gerontobiology of the human HFPU can best be translated into retardation or reversal of greying.

Does oxidative stress correlate with disease activity and severity in vitiligo? An analytical study

BACKGROUND

Oxidative damage to melanocytes, resulting from an imbalance between the damaging oxidative pathways and the protective anti-oxidants likely plays a pathogenic role in vitiligo.

AIM

To evaluate three parameters related to the oxidative stress (OS) pathway namely malondialdehyde (MDA), a marker of oxidative damage, and superoxide dismutase (SOD) and reduced glutathione (rGSH) (both antioxidants) in patients with active and stable vitiligo with either localized or generalized disease.

PATIENTS/METHODS

Sixty clinically diagnosed vitiligo patients were categorized into generalized (n = 30) or localized vitiligo (n = 30) and were further sub-grouped according to their disease activity into active and stable groups. Thirty healthy volunteers were included in the control group. ELISA was used for the evaluation of MDA, SOD, and r GSH.

RESULTS

The patient group demonstrated significantly raised levels of MDA and significantly decreased levels of SOD and rGSH compared with the control group. Further, the OS parameters were significantly more deranged in patients with generalized disease (all three-MDA, rGSH, and SOD) and an active disease (MDA) as compared to those with localized and stable disease, respectively.

CONCLUSION

Our findings suggest an important role of OS in relation to vitiligo activity and severity. Although the OS parameters were deranged in all subsets of patients, with respect to controls, the derangement of oxidative damage marker (MDA) in generalized and active disease groups was most marked. Disease remains active when the oxidative damage becomes higher but is unmatched with the anti-oxidant reserve which does not proportionately increase.

6-Shogaol Protects Human Melanocytes against Oxidative Stress through Activation of the Nrf2-Antioxidant Response Element Signaling Pathway

Skin is a major target of oxidative stress. Increasing evidence suggests that oxidative stress is the cause of melanocyte disappearance in vitiligo, which is an acquired pigmentary skin disorder characterized by patches of skin that have lost pigmentation. New herbal extracts with antioxidant activity are therefore being studied. 6-Shogaol (6-SG), an active compound from ginger, is capable of attenuating oxidative stress-induced ageing and neurotoxicity. Subsequently, to investigate whether 6-SG could protect melanocytes from oxidative stress, cultured human primary epidermal melanocytes (HEMn-MPs) were treated with hydrogen peroxide (H₂O₂) in the presence or absence of 6-SG. The 6-SG exhibited protective effects against H₂O₂-induced cell death by reducing oxidative stress. In addition, the 6-SG treatment activated the Nrf2-antioxidant response element signaling pathway by upregulating the mRNA expression of the antioxidant enzyme heme oxygenase 1 (HO-1), and protein expression of Nrf2, NAD(P)H: quinine oxidoreductase 1 (Nqo1), and HO-1. Furthermore, the 6-SG also displayed protective effects on melanocytes against Rhododendrol-induced oxidative stress. We concluded that 6-SG protects melanocytes against oxidative stress in vitro, and its protective effect is associated with the activation of the Nrf2-antioxidant response element signaling pathway. 6-SG, therefore, has potential for use in the prevention of melanocyte loss in the early stages of vitiligo or other pigmentary disorders.

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.

Are melanocortin peptides future therapeutics for cutaneous wound healing?

Cutaneous wound healing is a complex process divided into different phases, that is an inflammatory, proliferative and remodelling phase. During these phases, a variety of resident skin cell types but also cells of the immune system orchestrate the healing process. In the last year, it has been shown that the majority of cutaneous cell types express the melanocortin 1 receptor (MC1R) that binds α-melanocyte-stimulating hormone (α-MSH) with high affinity and elicits pleiotropic biological effects, for example modulation of inflammation and immune responses, cytoprotection, antioxidative defense and collagen turnover. Truncated α-MSH peptides such as Lys-Pro-Val (KPV) as well as derivatives like Lys-d-Pro-Thr (KdPT), the latter containing the amino acid sequence 193-195 of interleukin-1β, have been found to possess anti-inflammatory effects but to lack the pigment-inducing activity of α-MSH. We propose here that such peptides are promising future candidates for the treatment of cutaneous wounds and skin ulcers. Experimental approaches in silico, in vitro, ex vivo and in animal models are outlined. This is followed by an unbiased discussion of the pro and contra arguments of such peptides as future candidates for the therapeutic management of cutaneous wounds and a review of the so-far available data on melanocortin peptides and derivatives in wound healing.

Efficacy of an agonist of α-MSH, the palmitoyl tetrapeptide-20, in hair pigmentation

OBJECTIVE

Hair greying (i.e., canities) is a component of chronological ageing and occurs regardless of gender or ethnicity. Canities is directly linked to the loss of melanin and increase in oxidative stress in the hair follicle and shaft. To promote hair pigmentation and reduce the hair greying process, an agonist of α-melanocyte-stimulating hormone (α-MSH), a biomimetic peptide (palmitoyl tetrapeptide-20; PTP20) was developed. The aim of this study was to describe the effects of the designed peptide on hair greying.

METHODS

Effect of the PTP20 on the enzymatic activity of catalase and the production of H₂ O₂ by Human Follicle Dermal Papilla Cells (HFDPC) was evaluated. Influence of PTP20 on the expression of melanocortin receptor-1 (MC1-R) and the production of melanin were investigated. Enzymatic activity of sirtuin 1 (SIRT1) after treatment with PTP20 was also determined. Ex vivo studies using human micro-dissected hairs allowed to visualize the effect of PTP20 on the expression in hair follicle of catalase, TRP-1, TRP-2, Melan-A, ASIP, and MC1-R. These investigations were completed by a clinical study on 15 human male volunteers suffering from premature canities.

RESULTS

The in vitro and ex vivo studies revealed the capacity of the examined PTP20 peptide to enhance the expression of catalase and to decrease (30%) the intracellular level of H₂ O₂ . Moreover, PTP20 was shown to activate in vitro and ex vivo the melanogenesis process. In fact, an increase in the production of melanin was shown to be correlated with elevated expression of MC1-R, TRP-1, and Melan-A, and with the reduction in ASIP expression. A modulation on TRP-2 was also observed. The pivotal role of MC1-R was confirmed on protein expression analysed on volunteer's plucked hairs after 3 months of the daily application of lotion containing 10 ppm of PTP20 peptide.

CONCLUSION

The current findings demonstrate the ability of the biomimetic PTP20 peptide to preserve the function of follicular melanocytes. The present results suggest potential cosmetic application of this newly designed agonist of α-MSH to promote hair pigmentation and thus, reduce the hair greying process.

The catalase gene promoter and 5'-untranslated region variants lead to altered gene expression and enzyme activity in vitiligo

BACKGROUND

Oxidative stress is considered to be the initial event in the course of vitiligo. The enzyme catalase (CAT) is mainly involved in cellular defence against oxidizing agents through detoxifying H₂ O₂ .

OBJECTIVES

The aims were (i) to assess erythrocyte CAT enzyme activity and lipid peroxidation (LPO) levels as well as CAT mRNA expression in skin and blood; (ii) to investigate CAT gene promoter rs7943316, rs1001179, 5'-untranslated region rs1049982, and exon (rs17886350, rs11032709, rs17880442, rs35677492) polymorphisms; and (iii) to perform genotype/haplotype-phenotype correlation analyses in patients with vitiligo and controls from Gujarat.

METHODS

CAT activity and LPO levels were measured spectrophotometrically. CAT mRNA levels were estimated using real-time polymerase chain reaction (PCR) by the SYBR Green method. Single-nucleotide polymorphism genotyping was performed using PCR-restriction fragment length polymorphism and amplification-refractory mutation system-PCR analyses.

RESULTS

Patients with vitiligo showed significantly decreased CAT mRNA expression in lesional and nonlesional skin and in blood, with reduced CAT activity compared with that of controls. CAT -89A/T and -20T/C polymorphisms were significantly associated with patients, especially with active and generalized vitiligo, whereas no association was observed for -262G/A and exon polymorphisms. The A_-262 T_-89 C_-20 haplotype with variant alleles was found to be associated with 6·4-fold risk of vitiligo. Genotype/haplotype-phenotype correlation analyses revealed that individuals with susceptible genotypes/haplotype for CAT -89A/T and -20T/C polymorphisms showed significantly decreased CAT mRNA/activity, and only -89A/T polymorphisms showed significantly increased LPO levels compared with wild-type genotypes/haplotype.

CONCLUSIONS

The present study proposes the crucial role of CAT and its allelic variants in oxidative stress-mediated pathogenesis of vitiligo.

S100B Is a Potential Disease Activity Marker in Nonsegmental Vitiligo

Vitiligo is a chronic skin condition characterized by progressive depigmentation of the skin. S100B is a damage-associated molecular pattern protein expressed in melanocytes that has been proposed as a marker of melanocyte cytotoxicity. Although the use of S100B as a biomarker in melanoma is well established, to our knowledge its association with vitiligo activity has not yet been investigated. Here, we show that S100B serum levels were significantly increased in patients with active nonsegmental vitiligo and strongly correlated with the affected body surface area. Prospective follow-up showed a predictive value of serum S100B levels on disease progression. In vitro experiments using repeated freeze-thaw procedures showed an intracellular up-regulation of S100B in normal and vitiligo melanocytes before an extensive release in the environment. This phenomenon may explain the increased S100B serum values in the active phase of vitiligo. In a monobenzone-induced vitiligo mouse model we could show the potential of S100B inhibition as a therapeutic strategy in vitiligo. In conclusion, this report shows the possible use of S100B as a biomarker for disease activity in vitiligo. Our data suggest that this damage-associated molecular pattern protein could play a substantial role in the pathogenesis of vitiligo and may be a potential new target for treatment.

Vitiligo blood transcriptomics provides new insights into disease mechanisms and identifies potential novel therapeutic targets

BACKGROUND

Significant gaps remain regarding the pathomechanisms underlying the autoimmune response in vitiligo (VL), where the loss of self-tolerance leads to the targeted killing of melanocytes. Specifically, there is incomplete information regarding alterations in the systemic environment that are relevant to the disease state.

METHODS

We undertook a genome-wide profiling approach to examine gene expression in the peripheral blood of VL patients and healthy controls in the context of our previously published VL-skin gene expression profile. We used several in silico bioinformatics-based analyses to provide new insights into disease mechanisms and suggest novel targets for future therapy.

RESULTS

Unsupervised clustering methods of the VL-blood dataset demonstrate a "disease-state"-specific set of co-expressed genes. Ontology enrichment analysis of 99 differentially expressed genes (DEGs) uncovers a down-regulated immune/inflammatory response, B-Cell antigen receptor (BCR) pathways, apoptosis and catabolic processes in VL-blood. There is evidence for both type I and II interferon (IFN) playing a role in VL pathogenesis. We used interactome analysis to identify several key blood associated transcriptional factors (TFs) from within (STAT1, STAT6 and NF-kB), as well as "hidden" (CREB1, MYC, IRF4, IRF1, and TP53) from the dataset that potentially affect disease pathogenesis. The TFs overlap with our reported lesional-skin transcriptional circuitry, underscoring their potential importance to the disease. We also identify a shared VL-blood and -skin transcriptional "hot spot" that maps to chromosome 6, and includes three VL-blood dysregulated genes (PSMB8, PSMB9 and TAP1) described as potential VL-associated genetic susceptibility loci. Finally, we provide bioinformatics-based support for prioritizing dysregulated genes in VL-blood or skin as potential therapeutic targets.

CONCLUSIONS

We examined the VL-blood transcriptome in context with our (previously published) VL-skin transcriptional profile to address a major gap in knowledge regarding the systemic changes underlying skin-specific manifestation of vitiligo. Several transcriptional "hot spots" observed in both environments offer prioritized targets for identifying disease risk genes. Finally, within the transcriptional framework of VL, we identify five novel molecules (STAT1, PRKCD, PTPN6, MYC and FGFR2) that lend themselves to being targeted by drugs for future potential VL-therapy.

Stress-related skin disorders

Emerging research has suggested that the skin is not only a target of organismal distress but also an active participant of the stress response through production of local "HPA axis" components, peripheral nerve endings, and resident skin cells, including keratinocytes, mast cells, and immune/immune accessory cells. There are also bidirectional communication pathways between the brain and the skin, which play significant roles in integrating these interactions. In this review, we summarize the intricate relations between stress and several skin conditions. We have tried to identify the underlying mechanisms that link stress to the common dermatoses according to the latest scientific findings.

Chronic stress suppresses the expression of cutaneous hypothalamic-pituitary-adrenocortical axis elements and melanogenesis

Chronic stress can affect skin function, and some skin diseases might be triggered or aggravated by stress. Stress can activate the central hypothalamic–pituitary–adrenocortical (HPA) axis, which causes glucocorticoid levels to increase. The skin has HPA axis elements that react to environmental stressors to regulate skin functions, such as melanogenesis. This study explores the mechanism whereby chronic stress affects skin pigmentation, focusing on the HPA axis, and investigates the role of glucocorticoids in this pathway. We exposed C57BL/6 male mice to two types of chronic stress, chronic restraint stress (CRS) and chronic unpredictable mild stress (CUMS). Mice subjected to either stress condition showed reduced melanogenesis. Interestingly, CRS and CUMS triggered reductions in the mRNA expression levels of key factors involved in the HPA axis in the skin. In mice administered corticosterone, decreased melanin synthesis and reduced expression of HPA axis elements were observed. The reduced expression of HPA axis elements and melanogenesis in the skin of stressed mice were reversed by RU486 (a glucocorticoid receptor antagonist) treatment. Glucocorticoids had no significant inhibitory effect on melanogenesis in vitro. These results suggest that, high levels of serum corticosterone induced by chronic stress can reduce the expression of elements of the skin HPA axis by glucocorticoid-dependent negative feedback. These activities can eventually result in decreased skin pigmentation. Our findings raise the possibility that chronic stress could be a risk factor for depigmentation by disrupting the cutaneous HPA axis and should prompt dermatologists to exercise more caution when using glucocorticoids for treatment.

Association of the 389 C/T polymorphism of the catalase gene with susceptibility to vitiligo: a meta-analysis

BACKGROUND

The 389 C/T polymorphism in the catalase gene, CAT, has been reported to be associated with the risk of vitiligo.

AIM

To evaluate the association of the CAT 389 C/T polymorphism with susceptibility to vitiligo.

METHODS

We undertook a literature search and included the relevant studies passing the selection criteria. After the relevant data were extracted from each study, we statistically analysed the strength of association between the CAT gene and vitiligo risk.

RESULTS

In total, 7 relevant studies were identified, comprising 1531 patients with vitiligo and 1608 controls. The genotype distribution in the controls of all studies complied with Hardy-Weinberg equilibrium. After pooling all studies, the results indicated that the 389 C/T polymorphisms in CAT were not associated with the risk of vitiligo in Asians and Turks; however the CT genotype might be a genetic risk factor for susceptibility to vitiligo (OR = 1.77, 95% CI 1.30-2.43, P < 0.001) and the CC genotype might decrease the risk of vitiligo (OR = 0.63, 95% CI 0.47-0.86, P < 0.01) in western Europeans.

CONCLUSIONS

The 389 C/T polymorphisms in the CAT gene may be associated with vitiligo in western Europeans. Further studies with larger sample sizes are warranted to confirm our findings.

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.

Involvement of superoxide dismutase isoenzymes and their genetic variants in progression of and higher susceptibility to vitiligo

Oxidative stress has been implicated as the initial triggering event in vitiligo pathogenesis leading to melanocyte destruction. Here, we report a significant increase in oxidative stress in vitiligo patients as evidenced by high lipid peroxidation levels suggesting an imbalance in the antioxidant enzyme system as reported in our previous studies. This study examined the role of the enzymatic antioxidant SOD, which converts the pro-oxidant superoxide into H2O2, in vitiligo pathogenesis. The activity of three isoforms of SOD, i.e., SOD1, SOD2, and SOD3, was significantly higher in vitiligo patients. To identify the underlying mechanism for the increase in activities of SOD isoforms, we explored the SOD1, SOD2, and SOD3 genes for their genetic variations and transcript levels. The SOD2 Thr58Ile (rs35289490) and Leu84Phe (rs11575993) polymorphisms were significantly associated with vitiligo patients, and the Val16Ala (rs4880) polymorphism was associated with active vitiligo patients. Interestingly, SOD2 activity was contributed by these polymorphisms along with its increase in transcript levels in patients. SOD3 activity was associated with the Arg213Gly (rs8192291) polymorphism. The SOD3 transcript levels were also increased in patients, which might contribute to the increased SOD3 activity. However, we could not establish the genotype-phenotype correlation for SOD1 as we could not detect any novel or reported SNPs in SOD1. In addition, both transcript and protein levels of SOD1 were unchanged between patients and controls, though SOD1 activity was increased in patients. Activities of SOD isoforms also correlated with progression of the disease as the activity was higher in active cases of vitiligo compared to stable cases. Here, we report that SOD2 and SOD3 polymorphisms may be genetic risk factors for susceptibility and progression of vitiligo and hence the genetic makeup of an individual may form a basis for the effective treatment of the disease. Overall, our results suggest that increased activity of SOD isoforms under the influence of genetic factors may lead to accumulation of H2O2 in cytoplasmic, mitochondrial, and extracellular compartments resulting in oxidative damage to the melanocytes.

Key role of CRF in the skin stress response system

The discovery of corticotropin-releasing factor (CRF) or CRH defining the upper regulatory arm of the hypothalamic-pituitary-adrenal (HPA) axis, along with the identification of the corresponding receptors (CRFRs 1 and 2), represents a milestone in our understanding of central mechanisms regulating body and local homeostasis. We focused on the CRF-led signaling systems in the skin and offer a model for regulation of peripheral homeostasis based on the interaction of CRF and the structurally related urocortins with corresponding receptors and the resulting direct or indirect phenotypic effects that include regulation of epidermal barrier function, skin immune, pigmentary, adnexal, and dermal functions necessary to maintain local and systemic homeostasis. The regulatory modes of action include the classical CRF-led cutaneous equivalent of the central HPA axis, the expression and function of CRF and related peptides, and the stimulation of pro-opiomelanocortin peptides or cytokines. The key regulatory role is assigned to the CRFR-1α receptor, with other isoforms having modulatory effects. CRF can be released from sensory nerves and immune cells in response to emotional and environmental stressors. The expression sequence of peptides includes urocortin/CRF→pro-opiomelanocortin→ACTH, MSH, and β-endorphin. Expression of these peptides and of CRFR-1α is environmentally regulated, and their dysfunction can lead to skin and systemic diseases. Environmentally stressed skin can activate both the central and local HPA axis through either sensory nerves or humoral factors to turn on homeostatic responses counteracting cutaneous and systemic environmental damage. CRF and CRFR-1 may constitute novel targets through the use of specific agonists or antagonists, especially for therapy of skin diseases that worsen with stress, such as atopic dermatitis and psoriasis.

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.

Reduced serum paraoxonase-1 levels in vitiligo: further evidence of oxidative stress

Vitiligo is a common disorder that results in depigmented areas of the skin. The pathogenesis of the disease remains unclear, but oxidative stress is one suggested cause. Oxidative stress may be induced by increasing the generation of reactive oxygen species and other free radicals. The generation of reactive oxygen species is known to be associated with a decrease in antioxidant levels. This study examined oxidative stress index in active lesions of generalized vitiligo patients. We analysed serum levels of paraoxonase 1, arylesterase, catalase, ceruloplasmin, total antioxidant capacity, and oxidative stress index in patients with active lesions of generalized vitiligo, as well as in matched, healthy controls. Serum oxidants and oxidative stress indexes were higher, and serum antioxidants were lower, in vitiligo patients compared with healthy controls. Our findings suggest that oxidative stress may play an important role in the pathogenesis of vitiligo. Paraoxonase 1 can be used as an indicator in determining oxidative stress existent in the pathogenesis of vitiligo diseases.

Baicalein protects human melanocytes from H₂O₂-induced apoptosis via inhibiting mitochondria-dependent caspase activation and the p38 MAPK pathway

The removal of H(2)O(2) by antioxidants has been proven to be beneficial to patients with vitiligo. Baicalein (5,6,7-trihydroxyflavone; BE) has antioxidant activity and has been used in vitiligo therapy in Chinese traditional medicine. In this study, we investigated the potential protective effect and mechanisms of BE against H(2)O(2)-induced apoptosis in human melanocytes. Melanocytes from the PIG1 cell line were pretreated with different concentrations of BE for 1 h, followed by exposure to 1.0 mM H(2)O(2) for 24 h. Cell apoptosis, reactive oxygen species levels, and mitochondrial membrane potentials were evaluated by flow cytometry, and cell viability was determined by an MTT assay. The expressions of Bax, Bcl-2, caspase-3, total and phosphorylated ERKs, and p38 MAPK were assayed by Western blot to investigate the possible molecular mechanisms. Our results showed that BE significantly inhibited H(2)O(2)-induced apoptosis, intracellular reactive oxygen species generation, and changes in the mitochondrial membrane potential. It also reduced the Bax/Bcl-2 ratio, the release of cytochrome c, the activation of caspase-3, and the phosphorylation of p38 MAPK in a concentration-dependent manner. The results demonstrate for the first time that BE exerts a cytoprotective role in H(2)O(2)-induced apoptosis by inhibiting the mitochondria-dependent caspase activation and p38 MAPK pathway.

Aqueous extracts of the edible Gracilaria tenuistipitata are protective against H₂O₂-induced DNA damage, growth inhibition, and cell cycle arrest

Potential antioxidant properties of an aqueous extract of the edible red seaweed Gracilaria tenuistipitata (AEGT) against oxidative DNA damage were evaluated. The AEGT revealed several antioxidant molecules, including phenolics, flavonoids and ascorbic acid. In a cell-free assay, the extract exhibited 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity that significantly reduced H₂O₂-induced plasmid DNA breaks in a dose-response manner (P < 0.001). The AEGT also suppressed H₂O₂-induced oxidative DNA damage in H1299 cells by reducing the percentage of damaged DNA in a dose-response manner (P < 0.001) as measured by a modified alkaline comet-nuclear extract (comet-NE) assay. The MTT assay results showed that AEGT confers significant protection against H₂O₂-induced cytotoxicity and that AEGT itself is not cytotoxic (P < 0.001). Moreover, H₂O₂-induced cell cycle G2/M arrest was significantly released when cells were co-treated with different concentrations of AEGT (P < 0.001). Taken together, these findings suggest that edible red algae Gracilaria water extract can prevent H₂O₂-induced oxidative DNA damage and its related cellular responses.

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.

NF-κB knockdown can modulate amphetamine-mediated feeding response

This study determined if transcription factor NF-κB is involved in the effect of amphetamine (AMPH)-mediated feeding response. Moreover, possible roles of hypothalamic neuropeptide Y (NPY) and proopiomelanocortin (POMC) were also investigated. AMPH was administered daily to rats for four days. Changes in NF-κB, NPY and POMC expression were assessed and compared. The NPY gene was down-regulated with maximal response on Day 2 during AMPH treatment, which was consistent with the response to feeding behavior. In contrast, NF-κB and POMC genes were up-regulated, and their expression was increased by about 200% and 450%, respectively, with maximal response on Day 2. Moreover, NF-κB DNA binding ability and expression were increased similar to that of POMC. To examine further if NF-κB was involved, intracerebroventricular infusion of NF-κB antisense oligonucleotide was performed 1 h before the daily AMPH dosing in freely moving rats. Results showed that NF-κB knockdown could modify AMPH anorexia as well as NPY and POMC expression. The present findings prove that cerebral NF-κB participates in AMPH-mediated appetite suppression, possibly by modulating NPY and POMC expression. These results may aid in therapeutic research on AMPH and AMPH-like anti-obesity drugs.

Oxidative stress in ageing of hair

Experimental evidence supports the hypothesis that oxidative stress plays a major role in the ageing process. Reactive oxygen species are generated by a multitude of endogenous and environmental challenges. Reactive oxygen species or free radicals are highly reactive molecules that can directly damage cellular structural membranes, lipids, proteins, and DNA. The body possesses endogenous defence mechanisms, such as antioxidative enzymes and non-enzymatic antioxidative molecules, protecting it from free radicals by reducing and neutralizing them. With age, the production of free radicals increases, while the endogenous defence mechanisms decrease. This imbalance leads to the progressive damage of cellular structures, presumably resulting in the ageing phenotype. Ageing of hair manifests as decrease of melanocyte function or graying, and decrease in hair production or alopecia. There is circumstantial evidence that oxidative stress may be a pivotal mechanism contributing to hair graying and hair loss. New insights into the role and prevention of oxidative stress could open new strategies for intervention and reversal of the hair graying process and age-dependent alopecia.

tert-butyl hydroperoxide, an organic peroxide, causes temporary delay in hair growth in a neonatal rat model

tert-butyl hydroperoxide (tBHP), an organic peroxide, has been shown to cause irreversible damage to keratinocytes in vitro with prolonged administration at high concentrations, and reversible damage with short-term administration at low concentrations. To investigate the effects of tBHP on keratinocytes in vivo, we analysed hair growth in tBHP-treated neonatal rats. Sprague-Dawley and Long-Evans rat pups were injected subcutaneously with tBHP or vehicle once daily for 6 days, and hair growth was monitored. The tBHP-treated rats had a significant delay in hair growth. However, this delay reversed within days, and the hair coats, including hair pigmentation, of tBHP-treated and sham-treated rats were indistinguishable 2 weeks later. Histological analysis and BrdU labelling of S phase cells confirmed the delay in hair-follicle growth and its reversal in tBHP-treated rats. Our results indicated that the changes incurred in hair follicles by short-term use of high-dose oxidants in vivo are temporary and reversible.