Hypothesis: Possible Role for the Melatonin Receptor in Vitiligo: Discussion Paper

Genital lichen sclerosus and melanoma; a systematic review

Background

Lichen sclerosus (LSc) is a chronic, inflammatory, destructive skin disease with a predilection for the genitalia (GLSc). An association with vulval (Vu) and penile (Pe) squamous carcinoma (SCC) is now well established but melanoma (MM) has only rarely been reported complicating GLSc.

Methods

We have performed a systematic literature review of GLSc in patients with genital melanoma (GMM). Only articles that mentioned both GMM and LSc affecting either the penis or vulva were included.

Results

Twelve studies with a total of 20 patients were included. Our review shows that an association of GLSc with GMM has been more frequently reported in women and female children than men viz, 17 cases compared with three. It is notable that five of the cases (27.8%) concerned female children aged under twelve.

Discussion

These data suggest a rare association between GLSc and GMM. If proven, there arise intriguing questions about pathogenesis and consequences for counselling of patients and follow-up.

Revisiting the role of melatonin in human melanocyte physiology: A skin context perspective

The evolutionarily ancient methoxyindoleamine, melatonin, has long perplexed investigators by its versatility of functions and mechanisms of action, which include the regulation of vertebrate pigmentation. Although first discovered through its potent skin-lightening effects in amphibians, melatonin's role in human skin and hair follicle pigmentation and its impact on melanocyte physiology remain unclear. Synthesizing our limited current understanding of this role, we specifically examine its impact on melanogenesis, oxidative biology, mitochondrial function, melanocyte senescence, and pigmentation-related clock gene activity, with emphasis on human skin, yet without ignoring instructive pointers from nonhuman species. Given the strict dependence of melanocyte functions on the epithelial microenvironment, we underscore that melanocyte responses to melatonin are best interrogated in a physiological tissue context. Current evidence suggests that melatonin and some of its metabolites inhibit both, melanogenesis (via reducing tyrosinase activity) and melanocyte proliferation by stimulating melatonin membrane receptors (MT1, MT2). We discuss whether putative melanogenesis-inhibitory effects of melatonin may occur via activation of Nrf2-mediated PI3K/AKT signaling, estrogen receptor-mediated and/or melanocortin-1 receptor- and cAMP-dependent signaling, and/or via melatonin-regulated changes in peripheral clock genes that regulate human melanogenesis, namely Bmal1 and Per1. Melatonin and its metabolites also accumulate in melanocytes where they exert net cyto- and senescence-protective as well as antioxidative effects by operating as free radical scavengers, stimulating the synthesis and activity of ROS scavenging enzymes and other antioxidants, promoting DNA repair, and enhancing mitochondrial function. We argue that it is clinically and biologically important to definitively clarify whether melanocyte cell culture-based observations translate into melatonin-induced pigmentary changes in a physiological tissue context, that is, in human epidermis and hair follicles ex vivo, and are confirmed by clinical trial results. After defining major open questions in this field, we close by suggesting how to begin answering them in clinically relevant, currently available preclinical in situ research models.

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.

Recent Progress and Future Directions: The Nano-Drug Delivery System for the Treatment of Vitiligo

Vitiligo is a depigmentation disease that seriously affects the physical health, mental health and quality of life of a patient. Therapeutic aim at control immunoreaction by relieving oxidative stress. Unfortunately, the cuticle barrier function and lack of specific accumulation lead to unsatisfactory therapeutic outcomes and side effects. The introduction and innovation of nanotechnology offers inspiration and clues for the development of new strategies to treat vitiligo. However, not many studies have been done to interrogate how nanotechnology can be used for vitiligo treatment. In this review, we summarize and analyze recent studies involving nano-drug delivery systems for the treatment of vitiligo, with a special emphasis on liposomes, niosomes, nanohydrogel and nanoparticles. These studies made significant progress by either increasing drug loading efficiency or enhancing penetration. Based on these studies, there are three proposed principles for topical nano-drug delivery systems treatment of vitiligo including the promotion of transdermal penetration, enhancement of drug retention and facilitation of melanin regeneration. The presentation of these ideas may provide inspirations for the future development of topical drug delivery systems that will conquer vitiligo.

First record of atypical pigmentation pattern in fin whale Balaenoptera physalus in the Atlantic Ocean

Atypical pigmentation, which is rarely observed in the wild, may influence social interactions between animals and can be detrimental for survival. Hypopigmentation, which is the lack of pigment in a part or on the entire body, is a type of atypical pigmentation pattern that can be either acquired (e.g. vitiligo) or congenital resulting from the inheritance of mutations in pigment-related genes (e.g. albinism, leucism and piebaldism). This study documents atypical pigmentation in a fin whale Balaenoptera physalus off the northwestern coast of the Iberian Peninsula (Atlantic Ocean). Photographic and video data collected between 2016 and 2017 on 30 individual fin whales were examined. One fully-grown fin whale exhibited hypopigmentation. Several white patches of different shapes and sizes were present across the body of the fin whale including on the head, body, dorsal fin, flippers, and flukes. The position, shape, and lack of inflammation of the white patches on the whale observed, along with its body length and condition, might indicate that the depigmentation pattern is due to vitiligo. To our knowledge, this is the first case of atypical pigmentation pattern in fin whales described with photographs and video records. As these observations are rare, especially in highly migratory, long-lived, marine mammal species, this study provides valuable information to better understand the occurrence of this phenomenon. Further studies are needed to determine the ecological and physiological implications of atypical colourations, which might have a significant influence on the animal's survival.

Accounting for eXentricities: analysis of the X chromosome in GWAS reveals X-linked genes implicated in autoimmune diseases

Many complex human diseases are highly sexually dimorphic, suggesting a potential contribution of the X chromosome to disease risk. However, the X chromosome has been neglected or incorrectly analyzed in most genome-wide association studies (GWAS). We present tailored analytical methods and software that facilitate X-wide association studies (XWAS), which we further applied to reanalyze data from 16 GWAS of different autoimmune and related diseases (AID). We associated several X-linked genes with disease risk, among which (1) ARHGEF6 is associated with Crohn's disease and replicated in a study of ulcerative colitis, another inflammatory bowel disease (IBD). Indeed, ARHGEF6 interacts with a gastric bacterium that has been implicated in IBD. (2) CENPI is associated with three different AID, which is compelling in light of known associations with AID of autosomal genes encoding centromere proteins, as well as established autosomal evidence of pleiotropy between autoimmune diseases. (3) We replicated a previous association of FOXP3, a transcription factor that regulates T-cell development and function, with vitiligo; and (4) we discovered that C1GALT1C1 exhibits sex-specific effect on disease risk in both IBDs. These and other X-linked genes that we associated with AID tend to be highly expressed in tissues related to immune response, participate in major immune pathways, and display differential gene expression between males and females. Combined, the results demonstrate the importance of the X chromosome in autoimmunity, reveal the potential of extensive XWAS, even based on existing data, and provide the tools and incentive to properly include the X chromosome in future studies.

Metabolism of melatonin and biological activity of intermediates of melatoninergic pathway in human skin cells

Indolic and kynuric pathways of skin melatonin metabolism were monitored by liquid chromatography mass spectrometry in human keratinocytes, melanocytes, dermal fibroblasts, and melanoma cells. Production of 6-hydroxymelatonin [6(OH)M], N(1)-acetyl-N(2)-formyl-5-methoxykynuramine (AFMK) and 5-methoxytryptamine (5-MT) was detected in a cell type-dependent fashion. The major metabolites, 6(OH)M and AFMK, were produced in all cells. Thus, in immortalized epidermal (HaCaT) keratinocytes, 6(OH)M was the major product with Vmax = 63.7 ng/10(6) cells and Km = 10.2 μM, with lower production of AFMK and 5-MT. Melanocytes, keratinocytes, and fibroblasts transformed melatonin primarily into 6(OH)M and AFMK. In melanoma cells, 6(OH)M and AFMK were produced endogenously, a process accelerated by exogenous melatonin in the case of AFMK. In addition, N-acetylserotonin was endogenously produced by normal and malignant melanocytes. Metabolites showed selective antiproliferative effects on human primary epidermal keratinocytes in vitro. In ex vivo human skin, both melatonin and AFMK-stimulated expression of involucrin and keratins-10 and keratins-14 in the epidermis, indicating their stimulatory role in building and maintaining the epidermal barrier. In summary, the metabolism of melatonin and its endogenous production is cell type-dependent and expressed in all three main cell populations of human skin. Furthermore, melatonin and its metabolite AFMK stimulate differentiation in human epidermis, indicating their key role in building the skin barrier.

The melanocyte photosensory system in the human skin

The pigment cells form the largest population of neural crest cells to migrate into the epidermis and hair follicle along each dermatomic area from the neural folds. The melanopsin system responsible for photoentrainment, was isolated from the photosensitive dermal melanophores of frogs Xenopus laevis responding to light. Melanocytes form a photoresponsive network which reads the environmental seasonal variations in the light cycles in the same manner. The present work was undertaken to study the organization of this system by: I. Experimental assessment of photoresponse and II. Evidence of an organized system of photoreception in the skin. Melanocytes, in whole skin organ cultures and epidermal strips, from margin of vitiligo in G₂ phase show prominent dendricity, and express pigment, biogenic amines and hormones on UV exposure. The photoresponse depends on the photosensitive enzymes NAT/HIOMT and dopaoxidase. Melanocytes interact with adjacent keratinocytes, dermal capillaries, and nerve endings. The melanocyte network reads the diurnal and seasonal photophase by the melatonin/serotonin switch like the pineal. Sleep disorders and winter depression are corrected by phototherapy utilising this mechanism. Melanocytes showing photoactivity, aplasia, hypoplasia and hyperplasia, and interactive keratinocytes occupy the trigeminal, brachial and lumbosacral dermatomes, zones of high embryonic induction, forming an ectodermal placodal system. Melanin units and hair follicles serve as photoreceptors. Migration of active melanocytes to defined areas is evident in pigment patterns in guinea pigs. This study identifies defined photoreceptor melanocyte/epidermal domains which read the seasonal photophase and control the sleep waking cycle in response to the environmental light. I. Whole skin organ cultures, and epidermal strips from margin of vitiligo in G₂ phase are exposed to UV and IR to study sequential and dose response of marginal melanocytes, using histochemistry, immunohistochemistry to assess pigment, biogenic amines and hormones on UV exposure. II. Dermatomic Distributions: Detailed maps of melanocyte photoresponse in 356 biopsies, lesions in 297 vitiligo, 100 melanosis, 165 melanomas 142 leprosy and 442 basal cell/keratinocytes lesions were assessed for patterns of dermatomic distribution. Embryonal melanocyte migration along dermatomes was assessed in 285 guinea pigs from an inbred colony having black, brown and white patches.

Transcriptome analysis reveals markers of aberrantly activated innate immunity in vitiligo lesional and non-lesional skin

BACKGROUND

Vitiligo is characterized by the death of melanocytes in the skin. This is associated with the presence of T cell infiltrates in the lesional borders. However, at present, there is no detailed and systematic characterization on whether additional cellular or molecular changes are present inside vitiligo lesions. Further, it is unknown if the normal appearing non-lesional skin of vitiligo patients is in fact normal. The purpose of this study is to systematically characterize the molecular and cellular characteristics of the lesional and non-lesional skin of vitiligo patients.

METHODS AND MATERIALS

Paired lesional and non-lesional skin biopsies from twenty-three vitiligo patients and normal skin biopsies from sixteen healthy volunteers were obtained with informed consent. The following aspects were analyzed: (1) transcriptome changes present in vitiligo skin using DNA microarrays and qRT-PCR; (2) abnormal cellular infiltrates in vitiligo skin explant cultures using flow cytometry; and (3) distribution of the abnormal cellular infiltrates in vitiligo skin using immunofluorescence microscopy.

RESULTS

Compared with normal skin, vitiligo lesional skin contained 17 genes (mostly melanocyte-specific genes) whose expression was decreased or absent. In contrast, the relative expression of 13 genes was up-regulated. The up-regulated genes point to aberrant activity of the innate immune system, especially natural killer cells in vitiligo. Strikingly, the markers of heightened innate immune responses were also found to be up-regulated in the non-lesional skin of vitiligo patients.

CONCLUSIONS AND CLINICAL IMPLICATIONS

As the first systematic transcriptome characterization of the skin in vitiligo patients, this study revealed previously unknown molecular markers that strongly suggest aberrant innate immune activation in the microenvironment of vitiligo skin. Since these changes involve both lesional and non-lesional skin, our results suggest that therapies targeting the entire skin surface may improve treatment outcomes. Finally, this study revealed novel mediators that may facilitate future development of vitiligo therapies.

Melatonin membrane receptors in peripheral tissues: distribution and functions

Many of melatonin's actions are mediated through interaction with the G-protein coupled membrane bound melatonin receptors type 1 and type 2 (MT1 and MT2, respectively) or, indirectly with nuclear orphan receptors from the RORα/RZR family. Melatonin also binds to the quinone reductase II enzyme, previously defined the MT3 receptor. Melatonin receptors are widely distributed in the body; herein we summarize their expression and actions in non-neural tissues. Several controversies still exist regarding, for example, whether melatonin binds the RORα/RZR family. Studies of the peripheral distribution of melatonin receptors are important since they are attractive targets for immunomodulation, regulation of endocrine, reproductive and cardiovascular functions, modulation of skin pigmentation, hair growth, cancerogenesis, and aging. Melatonin receptor agonists and antagonists have an exciting future since they could define multiple mechanisms by which melatonin modulates the complexity of such a wide variety of physiological and pathological processes.

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.

Vitiligo, reactive oxygen species and T-cells

The acquired depigmenting disorder of vitiligo affects an estimated 1% of the world population and constitutes one of the commonest dermatoses. Although essentially asymptomatic, the psychosocial impact of vitiligo can be severe. The cause of vitiligo remains enigmatic, hampering efforts at successful therapy. The underlying pathogenesis of the pigment loss has, however, been clarified to some extent in recent years, offering the prospect of effective treatment, accurate prognosis and rational preventative strategies. Vitiligo occurs when functioning melanocytes disappear from the epidermis. A single dominant pathway is unlikely to account for all cases of melanocyte loss in vitiligo; rather, it is the result of complex interactions of biochemical, environmental and immunological events, in a permissive genetic milieu. ROS (reactive oxygen species) and H2O2 in excess can damage biological processes, and this situation has been documented in active vitiligo skin. Tyrosinase activity is impaired by excess H2O2 through oxidation of methionine residues in this key melanogenic enzyme. Mechanisms for repairing this oxidant damage are also damaged by H2O2, compounding the effect. Numerous proteins and peptides, in addition to tyrosinase, are similarly affected. It is possible that oxidant stress is the principal cause of vitiligo. However, there is also ample evidence of immunological phenomena in vitiligo, particularly in established chronic and progressive disease. Both innate and adaptive arms of the immune system are involved, with a dominant role for T-cells. Sensitized CD8+ T-cells are targeted to melanocyte differentiation antigens and destroy melanocytes either as the primary event in vitiligo 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 present review focuses on the scientific evidence linking alterations in ROS and/or T-cells to vitiligo.

The role of T cells in cutaneous autoimmune disease

T cells assume a fundamental function in immunosurveillance and maintenance of the cutaneous immune barrier, yet derangement of their requisite role effects a range of cutaneous autoimmune diseases with significant associated morbidity. While blistering skin diseases, such as pemphigus vulgaris (PV), pemphigus foliaceus (PF) and bullous pemphigoid (BP) are mediated by antibodies directed against autoantigens found in the skin, recent evidence has shown that T cell activation is crucial for the initiation and coordination of this humoral response. Non-blistering skin diseases, such as alopecia areata (AA), vitiligo (VL) and psoriasis (PS) are increasingly believed to be directly mediated by the activities of autoreactive T cells. Here, we examine T lymphocyte control of antibody-mediated and cell-mediated processes involved in the pathoimmunology of the above mentioned skin diseases.

Hypopigmenting agents: an updated review on biological, chemical and clinical aspects

An overview of agents causing hypopigmentation in human skin is presented. The review is organized to put forward groups of biological and chemical agents. Their mechanisms of action cover (i) tyrosinase inhibition, maturation and enhancement of its degradation; (ii) Mitf inhibition; (iii) downregulation of MC1R activity; (iv) interference with melanosome maturation and transfer; (v) melanocyte loss, desquamation and chemical peeling. Tyrosinase inhibition is the most common approach to achieve skin hypopigmentation as this enzyme catalyses the rate-limiting step of pigmentation. Despite the large number of tyrosinase inhibitors in vitro, only a few are able to induce effects in clinical trials. The gap between in-vitro and in-vivo studies suggests that innovative strategies are needed for validating their efficacy and safety. Successful treatments need the combination of two or more agents acting on different mechanisms to achieve a synergistic effect. In addition to tyrosinase inhibition, other parameters related to cytotoxicity, solubility, cutaneous absorption, penetration and stability of the agents should be considered. The screening test system is also very important as keratinocytes play an active role in modulating melanogenesis within melanocytes. Mammalian skin or at least keratinocytes/melanocytes co-cultures should be preferred rather than pure melanocyte cultures or soluble tyrosinase.

A review and a new hypothesis for non-immunological pathogenetic mechanisms in vitiligo

Vitiligo is an acquired depigmenting disorder characterized by the loss of functioning epidermal melanocytes because of multifactorial and overlapping pathogenetic mechanisms. Besides the immunological approach, the study of the metabolic deregulations leading to toxic damage of the melanocytes appears to be more and more relevant. It was only last year that the first in vitro evidence supporting the link and the temporal sequence between the immune response and the cellular oxidative stress was provided, suggesting that the intrinsic damage of the melanocytes is primitive. What can be the guide line of the multiple altered metabolisms? A compromised membrane could render the cell sensitive to the external and internal agents differently, usually ineffective on the cell activity and survival. The primitive altered arrangement of the lipids may affect the transmembrane housing of proteins with enzymatic or receptorial activities, also conferring on them antigenic properties.

Melanin pigmentation in mammalian skin and its hormonal regulation

Cutaneous melanin pigment plays a critical role in camouflage, mimicry, social communication, and protection against harmful effects of solar radiation. Melanogenesis is under complex regulatory control by multiple agents interacting via pathways activated by receptor-dependent and -independent mechanisms, in hormonal, auto-, para-, or intracrine fashion. Because of the multidirectional nature and heterogeneous character of the melanogenesis modifying agents, its controlling factors are not organized into simple linear sequences, but they interphase instead in a multidimensional network, with extensive functional overlapping with connections arranged both in series and in parallel. The most important positive regulator of melanogenesis is the MC1 receptor with its ligands melanocortins and ACTH, whereas among the negative regulators agouti protein stands out, determining intensity of melanogenesis and also the type of melanin synthesized. Within the context of the skin as a stress organ, melanogenic activity serves as a unique molecular sensor and transducer of noxious signals and as regulator of local homeostasis. In keeping with these multiple roles, melanogenesis is controlled by a highly structured system, active since early embryogenesis and capable of superselective functional regulation that may reach down to the cellular level represented by single melanocytes. Indeed, the significance of melanogenesis extends beyond the mere assignment of a color trait.

Vitiligo

O vitiligo é doença de pele de causa desconhecida que acomete cerca de 1% da população, comprometendo de modo semelhante homens e mulheres, preferencialmente entre 10 e 30 anos de idade. Alguns fatores precipitantes para essa doença são: estresse físico e emocional, traumas mecânicos e substâncias químicas, como derivados do fenol. Doenças auto-imunes, principalmente as tireoidianas, podem estar associadas ao vitiligo. Novas terapias têm sido propostas, como o uso de imunomoduladores tópicos, aliadas àquelas já consolidadas, como os psoralenos e os corticosteróides; o sucesso terapêutico, entretanto, está estritamente relacionado à qualidade da relação médico/paciente.

Expression of hypothalamic-pituitary-thyroid axis related genes in the human skin

The skin is commonly affected in thyroid diseases, but the mechanism for this association is still unclear. As the skin expresses numerous neuroendocrine elements, we tested the additional cutaneous expression of mediators operating in the hypothalamic-pituitary-thyroid axis. We found significant expression of the thyroid-stimulating hormone receptor mRNA in cultured keratinocytes, epidermal melanocytes, and melanoma cells. The presence of thyroid-stimulating hormone receptor was confirmed by northern analyses and the thyroid-stimulating hormone receptor was found to be functionally active in cyclic adenosine monophosphate signal assays. Thyroid-stimulating hormone receptor expressing cells also expressed the sodium iodide symporter and thyroglobulin genes. We also found expression of deiodinases 2 and 3 (mainly deiodinase 2) in whole skin biopsy specimens, and in the majority of epidermal and dermal cells by reverse transcription-polymerase chain reaction followed by sequencing of the amplified gene segments. There was selective expression of the gene for thyroid-stimulating hormone beta; detection of the thyroid-releasing hormone gene was minimal and thyroid-releasing hormone receptor mRNA was not detected in most of the samples. Expression of functional thyroid-stimulating hormone receptor in the skin may have significant physiologic and pathologic consequences, particularly in autoimmune conditions associated with production of stimulating antibodies against the thyroid-stimulating hormone receptor. We conclude that the expanding list of neuroendocrine elements expressed in the skin supports a strong role for this system in cutaneous biology.

Vulvar malignant melanoma associated with human papillomavirus DNA: report of two cases and review of literature

Oncogenic human papillomavirus (HPV) types such as HPV 16 are known to play a crucial role in the development of anogenital carcinomas. The etiology of anogenital malignant melanoma is unknown. We report two case of vulvar malignant melanoma in which multiple HPV types including HPV 16 and putative novel HPV types (alb-1, alb-2, alb-7, and alb-10) were identified by degenerated nested polymerase chain techniques (polymerase chain reaction) in both the malignant melanoma and surrounding skin. One melanoma was associated with lichen sclerosus, and the other, with melanoma in situ and pigmented vulvar squamous papillomatosis. These melanomas harbored HPV types alb-7, and HPV 16 as well as alb-1, respectively. HPV types 16, 20, 21, 36, alb-2, and AJ001060 were detected in vulvar skin affected by lichen sclerosus. Vulvar squamous papillomatosis harbored HPV types 28 and alb-10. HPV 16 was physically integrated into the host genome in lichen sclerosus skin and possibly in the melanoma associated with pigmented vulvar squamous papillomatosis. Twenty-two percent (4 of 18) of normal control specimens from skin tumor excisions were found to harbor HPV DNA (HPV types 3, 54, and alb-7); none of these control samples harbored multiple HPV DNA. These findings of multiple HPV DNA and integrated HPV 16 in skin associated with vulvar malignant melanoma indicate that HPV may play a role in the development of vulvar malignant melanoma. The role of HPV could be either direct through infection of melanocytes or indirect as a cofactor with free radicals in chronic fibroinflammatory vulvar disorders such as lichen sclerosus.

Possible mechanisms of hypopigmentation in lichen sclerosus

Lichen sclerosus (LS) shares with vitiligo a milky-white appearance. By biopsy, pathognomonic dermal sclerosis readily distinguishes LS from vitiligo and other causes of leukoderma. To determine what the mechanism of hypopigmentation is in LS, we examined samples from LS cases for alterations in melanin content (Fontana-Masson stain) and melanocyte number (HMB-45 [PMEL-17/gp100], Mel-5 [TRP-1], Mart-1 [Melan A]) and compared these findings with those in controls of normal skin, acute scars, vitiligo, and lichen planus (LP; a common inflammatory cause of hyperpigmentation). The degree and extent of melanization found in LS overlapped with that in acute scars showing predominantly hypomelanized keratinocytes, with that in LP containing regions with numerous melanophages, and with that in vitiligo exhibiting focal regions of keratinocytes devoid of melanin pigment. By hematoxylin-eosin staining and immunocytochemistry for Mel-5 and Mart-1, LS had a lower mean count of melanocytes than acute scars, LP, and normal skin per 200 basal keratinocytes. In addition, a few LS cases had a significant loss of melanocytes comparable to that of vitiligo. Surprisingly, Mart-1 identified rare melanocytes in 67% of vitiligo cases and a significantly larger pool of melanocytes in LS and controls other than those labeled by Mel-5. Furthermore, LP and evolving lesions of LS contained the highest Mart-1 counts. HMB-45-immunoreactive melanocytes were found in the majority of acute scars and in LP and late-stage LS lesions at significantly lower levels than Mel-5- and Mart-1- labeled melanocytes, but they were not found in vitiligo or normal skin. We propose that several mechanisms may play a role in the production of leucoderma in LS: 1) decreased melanin production; 2) block in transfer of melanosomes to keratinocytes; and 3) melanocyte loss. The latter finding may be the pathogenic connection (lichenoid dermatitis of LS triggering an autoimmune reaction to melanocytes) that underlies the documented association of LS with vitiligo.

Vitiligo. Pathogenesis and treatment

Vitiligo is an acquired skin disorder caused by the disappearance of pigment cells from the epidermis that gives rise to well defined white patches which are often symmetrically distributed. The lack of melanin pigment makes the lesional skin more sensitive to sunburn. Vitiligo can be cosmetically disfiguring and it is a stigmatizing condition, leading to serious psychologic problems in daily life. It occurs worldwide in about 0.5% of the population and it occurs as frequently in males as it does in females. The cause is unknown, but might involve genetic factors, autoimmunity, neurologic factors, toxic metabolites, and lack of melanocyte growth factors. Since a causative (gene) treatment is not (yet) available, current modalities are directed towards stopping progression and to achieving repigmentation in order to repair the morphology and functional deficiencies of the depigmented skin areas. Many treatments have been used for some time; however; there are some new developments: narrowband ultraviolet (UV) B (311 nm) therapy, the combination of corticosteroid cream + UVA therapy, and the transplantation of autologous pigment cells in various modalities. In widespread vitiligo, residual pigment can be removed by depigmentation agents. Sunscreens, camouflage products, and good guidance may help the patient cope better with the disease.

Impact of life events on the onset of vitiligo in adults: preliminary evidence for a psychological dimension in aetiology

The present study retrospectively examines the role of stressful life events in the onset of vitiligo in adults. A matched clinical sample of patients with other forms of disfigurement or skin disease (dystrophic epidermolysis bullosa and naevi, not thought to be associated with stress) served as a control group. Newly diagnosed patients and matched controls were thus asked to complete the 12-month version of the Schedule of Recent Experience, a questionnaire which measures the frequency and number of stressful life events occurring over a specified period. The results suggest that such patients endure a significantly higher number of stressful life events than do controls, suggesting that psychological distress may have contributed to the onset of their condition. The implications of the results are discussed and suggestions made for future research.

Peripheral T-cell activation in non-segmental vitiligo

Vitiligo is a hypopigmentary dermatosis of probable autoimmune origin. Previously reported aberrations in peripheral blood mononuclear cells (PBMC), especially T cells and T cell subsets, have been inconsistent. Lymphocyte subpopulations were examined using flow cytometry and monoclonal antibodies against CD4, CD8, CD20, CD25, CD45RA, and HLA-DR in 34 patients with non-segmental vitiligo. Twelve patients had not received any previous treatment and 22 had previously received at least one course of PUVA therapy that was discontinued at least four months prior to our study. Compared to matched controls, we found significant increases in CD25 and HLA-DR in vitiligo patients (p = 0.000). An inverse correlation was observed between HLA-DR and patient status with regard to treatment (p = 0.001). These results suggest a role for T cells in the pathogenesis of vitiligo and imply that previous PUVA therapy may be reflected by an alteration in circulating DR +ve cells.

Pharmacological disruption of hair follicle pigmentation by cyclophosphamide as a model for studying the melanocyte response to and recovery from cytotoxic drug damage in situ

Here we show that cyclophosphamide induces disruption of follicular melanogenesis, which is characterized by abnormal transfer of pigment granules to ectopic hair bulb locations, extrafollicular melanin incontinence, disordered formation of melanosomes, and inhibition of melanosome transfer into precortical keratinocytes. This is in contrast to dexamethasone-induced termination of follicle melanogenesis, which activates premature but predominantly normal catagen development. Cyclophosphamide-induced pigmentation disruption was accompanied by significant alterations of biochemical and biophysical markers of melanogenesis, compared to control mice treated either with vehicle or with topical dexamethasone. Electron paramagnetic resonance spectroscopy shows a decline in the melanin signal and predominant eumelanin production. Tyrosine hydroxylase activity of tyrosinase and dihydroxyphenylalanine oxidation drop rapidly, while DOPAchrome tautomerase activity increases and dihydroxyindole carboxylic acid conversion factor activity remains unchanged in cyclophosphamide-treated mice compared to controls. These observations emphasize the key role of tyrosinase as opposed to postdihydroxyphenylalanine oxidase steps in normal and pathological termination of melanogenesis and shows that tyrosinase is the most sensitive target of the melanogenic apparatus for pharmacological regulation. Follicle pigmentation recovers only during the subsequent hair cycle, i.e., after a new anagen hair bulb has been constructed, which points to the existence of a relatively chemoresistant melanoblast-like cell population residing in the noncycling part of the hair follicle.

Morphologic observations on the dermal nerves in vitiligo: an ultrastructural study

BACKGROUND

Vitiligo is a common idiopathic skin disorder. The etiology is unknown, although various hypotheses have been advanced. These include the neuronal hypothesis, where neuronal factors are thought to play a role in the pathogenesis of this disease.

METHODS

Skin biopsies were taken from marginal and central parts of four vitiligo patients. Biopsies were also taken from nonvitiliginous skin of each patient and from four normal control subjects. Sections were examined under the electron-microscope. Nerve fibers in the superficial dermis were examined.

RESULTS

Subtle ultrastructural changes, including regeneration and degeneration, were consistently found in dermal nerves of vitiligo lesions. The most consistent feature, seen in all four vitiligo patients studied (in both lesional and marginal areas), was an increased thickness of the basement membrane of Schwann cells. This change was found in approximately three-quarters of all dermal nerves in vitiligo biopsies, but in only about one-quarter of dermal nerves in normal control skin. About half the abnormal dermal nerves in vitiligo skin showed minor axonal damage, although indicators of regeneration (increased mitochondria and rough endoplasmic reticulum) predominated. The dermal nerves in vitiligo showed no difference in fiber diameter or fiber density in comparison with controls.

CONCLUSIONS

In vitiligo both axonal degeneration and nerve regeneration may occur, with the latter possibly being a reactive change to earlier axonal damage. These findings support the hypothesis that there is a neuronal component to this disease.

Neuropeptide and neuronal marker studies in vitiligo

Neuropeptide and neuronal marker immunoreactivity was studied in skin biopsies from lesional and marginal areas in 12 patients with vitiligo, and in seven normal controls. The vitiligo was active in seven, static in two, and of unknown activity in three. Antibodies against general neuronal marker PGP 9.5 (PGP 9.5), substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), and neuropeptide Y (NPY), were used. The epidermis, dermo-epidermal junction, papillary and reticular dermis, and appendages, were assessed semiquantitatively for reactivity with each antibody. Staining with PGP 9.5 in the upper dermis was assessed quantitatively by image analysis. An increase in reactivity against NPY antibody was seen in five of 10 cases (three with active vitiligo) in the marginal areas, and in three of 12 subjects (all with active vitiligo) in the lesional vitiligo areas. VIP antibody reactivity showed a minimal increase in the marginal and lesional vitiligo areas (in two cases each, both of whom had active vitiligo). SP and CGRP reactivities did not differ from normal. PGP 9.5 staining was minimally increased at the dermo-epidermal junction and lower Malpighian layer in biopsies from marginal areas in three of 10 subjects (all with active vitiligo). Quantitative analysis of PGP 9.5 reactivity in the upper dermis showed no difference between vitiligo and normal biopsies. These findings support the concept of neuronal or neuropeptide involvement in vitiligo, and in particular suggest that NPY may have a role in the pathogenesis of the disease.

Murine skin as a target for melatonin bioregulation

Specific binding sites for 3H-melatonin were detected in membrane fractions prepared from C57 BL-6 mouse skin, and were localized to the epidermis and the epithelial bulb of the hair follicle by in situ autoradiography. In skin organ culture, melatonin stimulated DNA synthesis by the epidermal keratinocytes at concentration 0.1-10 nM, while at > or = 1 microM it inhibited tyrosinase activity. We concluded that murine skin is a target for melatonin bioregulation.

Identification and characterization of two isozymic forms of arylamine N-acetyltransferase in Syrian hamster skin

Arylamine N-acetyltransferase (EC 2.3.1.5) activity was examined using skin from Syrian hamster. Two isozymes of arylamine N-acetyltransferase, designated NAT-1 and NAT-2, were detected on anion-exchange high-performance liquid chromatography analysis. Both enzyme activities had indistinguishable molecular masses (30 kDa), but differed significantly in their specificity toward the aromatic amines including serotonin, dopamine, methoxytryptamine, tryptamine, para-phenetidine, para-aminobenzoic acid, and sulphamethazine. Specifically, NAT-2 but not NAT-1 catalyzed acetylation of dopamine to N-acetyldopamine and acetylation of serotonin to form N-acetylserotonin, a direct precursor of melatonin. The two isozymes were also distinguishable based upon their sensitivity toward methotrexate inhibition (50% inhibiting dose for NAT-1 = 380 microM; NAT-2 > 2 mM). The presence of these two activities in the skin raises new questions about the physiologic role of this enzyme in general and in the skin-specific functions in particular.

Review of the etiopathomechanism of vitiligo: a convergence theory

Vitiligo is an acquired melanin pigmentary disorder manifesting itself by expanding depigmented lesions of the skin. To date, the etiopathomechanism of vitiligo has not been convincingly elucidated and a number of seemingly mutually opposed hypotheses with equal likelihood still coexist. Concurrent theories on vitiligo etiology, together with supportive evidence, are reviewed here. Due to the observed variation in clinical manifestations of the disease, it seems likely that the etiology of vitiligo may differ among patients. Therefore several theories on vitiligo etiopathogenesis have been combined to formulate a convergence theory for vitiligo, also presented in this article. This theory states that stress, accumulation of toxic compounds, infection, autoimmunity, mutations, altered cellular environment and impaired melanocyte migration and/or proliferation can all contribute to vitiligo etiopathogenesis in varying proportions.

Melanogenesis is coupled to murine anagen: toward new concepts for the role of melanocytes and the regulation of melanogenesis in hair growth

Hair is actively pigmented only when it grows: the melanogenic activity of follicular melanocytes (MC) is strictly coupled to the anagen stage of the hair cycle. In catagen, melanin formation is switched off and is absent throughout telogen. The appearance of pigmentation is preceded, and further accompanied by, a time-frame - restricted, differential pattern of tyrosinase transcription, translation, and enzyme activities during the development of anagen follicles. In this speculative review, we argue that signals required for melanin synthesis and pigment transfer to bulb keratinocytes (KC) are intrinsic to the skin, rather than coming from the serum. First, the proopiomelanocortin (POMC) gene is expressed and translated during anagen, but is below the level of detectability in telogen; POMC is a precursor protein for adrenocorticotropin and melanotropins, which are potent regulators of MC proliferation and differentiation. Second, fibroblasts and KC produce factors that affect MC proliferation and differentiation. We suggest that signals regulating follicular MC activity partially derive from cutaneous cells expressing POMC. Vice versa, MC transfer to surrounding KC pigment granules with potent bioregulatory properties. MC also produce and secrete various signal molecules that can regulate mesenchymal and epithelial cell functions. Anagen-associated melanogenesis and the cyclic production of a pigmented hair shaft result from programmed and tightly coordinated epithelial-mesenchymal-neuroectodermal interactions, in which MC may act not only as pigmentary, but also as hair growth-regulatory cells.

Vitiligo: where do we stand?

Vitiligo is a puzzling disorder characterized by a disappearance of epidermal and/or follicular melanocytes by unknown mechanisms. This very common disorder involving 1-4% of the world population is thus of great importance for the practicing dermatologist. The cellular and molecular mechanisms leading to the destruction of melanocytes in this disorder have not yet been elucidated, making it of major interest for the cell biologist involved in melanocyte research. Recent advances in this field, due largely to the availability of techniques for culturing normal human melanocytes, opened new perspectives in the understanding of vitiligo. Although vitiligo has long been considered a disorder confined to the skin, there is now good evidence that it also involves the extracutaneous compartment of the "melanocyte organ." It is also clear that vitiligo is not only a melanocyte disorder, but that it also involves cells, such as keratinocytes and Langerhans cells, found in the epidermis and follicular epithelium. The three prevailing theories of the pathogenesis of vitiligo are the immune hypothesis, the neural hypothesis, and the self-destruct hypothesis. New hypotheses suggest that vitiligo may be due to (1) a deficiency in an unidentified melanocyte growth factor, (2) an intrinsic defect of the structure and function of the rough endoplasmic reticulum in vitiligo melanocytes, (3) abnormalities in a putative melatonin receptor on melanocytes and (4) a breakdown in free radical defense in the epidermis. None of these hypotheses has been demonstrated, and according to the available data, it is likely that the loss of epidermal and follicular melanocytes in vitiligo may be the result of several different pathogenetic mechanisms.

Ultrastructural observations on the hair bulb melanocytes and melanosomes in acute alopecia areata

It is well recognized that alopecia areata (Aa) may preferentially affect pigmented hair and may spare white hair, and that regrowing hair in the disease is often initially white. In addition, there is an association with vitiligo and ocular depigmentation. To date, the pathomechanisms of the melanocyte effects are unclear. We have studied 10 patients with untreated acute alopecia areata, and three normal patients without hair loss. Morphologic changes, studied by conventional light and electron microscopy, in the cytoplasm of affected melanocytes often predated nuclear hyperchromatism. Increased numbers of bizarre melanosomes were found in affected melanocytes compared with normal ones; such melanosomes had incomplete or "aborted" melanization, resulting in poor pigment deposition, and were disrupted, enlarged and rounded, with loss of normal ellipsoidal shape. An unusual outer root sheath (ORS) distribution of hair bulb melanocytes was seen. Other atypical melanosome effects included marked pigment displacement into peribulbar and DP melanophages. In the DP clumped melanin granules formed giant spherical complexes without discernible limiting membranes, which were sometimes associated with lymphocytes. These morphologic changes indicate an active involvement of hair bulb melanocytes in alopecia areata.