Catecholamines increase in the urine of non-segmental vitiligo especially during its active phase

The Urinary Metabolome of Newborns with Perinatal Complications

Maternal pathological conditions such as infections and chronic diseases, along with unexpected events during labor, can lead to life-threatening perinatal outcomes. These outcomes can have irreversible consequences throughout an individual's entire life. Urinary metabolomics can provide valuable insights into early physiological adaptations in healthy newborns, as well as metabolic disturbances in premature infants or infants with birth complications. In the present study, we measured 180 metabolites and metabolite ratios in the urine of 13 healthy (hospital-discharged) and 38 critically ill newborns (admitted to the neonatal intensive care unit (NICU)). We used an in-house-developed targeted tandem mass spectrometry (MS/MS)-based metabolomic assay (TMIC Mega) combining liquid chromatography (LC-MS/MS) and flow injection analysis (FIA-MS/MS) to quantitatively analyze up to 26 classes of compounds. Average urinary concentrations (and ranges) for 167 different metabolites from 38 critically ill NICU newborns during their first 24 h of life were determined. Similar sets of urinary values were determined for the 13 healthy newborns. These reference data have been uploaded to the Human Metabolome Database. Urinary concentrations and ranges of 37 metabolites are reported for the first time for newborns. Significant differences were found in the urinary levels of 44 metabolites between healthy newborns and those admitted at the NICU. Metabolites such as acylcarnitines, amino acids and derivatives, biogenic amines, sugars, and organic acids are dysregulated in newborns with bronchopulmonary dysplasia (BPD), asphyxia, or newborns exposed to SARS-CoV-2 during the intrauterine period. Urine can serve as a valuable source of information for understanding metabolic alterations associated with life-threatening perinatal outcomes.

Circulating Exosomal miR-493-3p Affects Melanocyte Survival and Function by Regulating Epidermal Dopamine Concentration in Segmental Vitiligo

Circulating exosomal microRNAs have been used as potential biomarkers for various disorders. However, to date, the microRNA expression profile of circulating exosomes in patients with segmental vitiligo (SV) has not been identified. Thus, we aimed to identify the expression profile of circulating exosomal microRNAs and investigate their role in the pathogenesis of SV. Our study identified the expression profile of circulating exosomal microRNAs in SV and selected miR-493-3p as a candidate biomarker whose expression is significantly increased in circulating exosomes and perilesions in patients with SV. Circulating exosomes were internalized by human primary keratinocytes and increased dopamine secretion in vitro. Furthermore, miR-493-3p overexpression in keratinocytes increased dopamine concentration in the culture supernatant, which led to a significant increase in ROS and melanocyte apoptosis as well as a decrease in melanocyte proliferation and melanin synthesis in the coculture system by targeting HNRNPU. We also confirmed that HNRNPU could bind to and regulate COMT, a major degradative enzyme of dopamine. Hence, circulating exosomal miR-493-3p is a biomarker for SV, and the miR-493-3p/HNRNPU/COMT/dopamine axis may contribute to melanocyte dysregulation in the pathogenesis of SV.

Molecular Probes, Chemosensors, and Nanosensors for Optical Detection of Biorelevant Molecules and Ions in Aqueous Media and Biofluids

Synthetic molecular probes, chemosensors, and nanosensors used in combination with innovative assay protocols hold great potential for the development of robust, low-cost, and fast-responding sensors that are applicable in biofluids (urine, blood, and saliva). Particularly, the development of sensors for metabolites, neurotransmitters, drugs, and inorganic ions is highly desirable due to a lack of suitable biosensors. In addition, the monitoring and analysis of metabolic and signaling networks in cells and organisms by optical probes and chemosensors is becoming increasingly important in molecular biology and medicine. Thus, new perspectives for personalized diagnostics, theranostics, and biochemical/medical research will be unlocked when standing limitations of artificial binders and receptors are overcome. In this review, we survey synthetic sensing systems that have promising (future) application potential for the detection of small molecules, cations, and anions in aqueous media and biofluids. Special attention was given to sensing systems that provide a readily measurable optical signal through dynamic covalent chemistry, supramolecular host-guest interactions, or nanoparticles featuring plasmonic effects. This review shall also enable the reader to evaluate the current performance of molecular probes, chemosensors, and nanosensors in terms of sensitivity and selectivity with respect to practical requirement, and thereby inspiring new ideas for the development of further advanced systems.

Role of Amine Neurotransmitters and Their Receptors in Skin Pigmentation: Therapeutic Implication

Skin pigmentation can occur due to increased melanin, including melanocyte proliferation, melanin biosynthesis, or melanocyte migration. There are many factors that influence the melanin production process, but the role of neurotransmitters in this process is still unclear. We found that histamine and serotonin influence the different stages of melanogenesis and melanogenesis, which increase melanogenesis. Since then, several related papers have been published, and from these papers, it has been recognised that the role of neurotransmitters in skin-pigment-related diseases needs to be summarised. By introducing the role of neurotransmitters in the regulation of various pigment disorders, including vitiligo and melasma, through this review, many researchers can be expected to try to apply neurotransmitter-related agonists and antagonists as treatments for skin pigment disorders.

Carvedilol, an Adrenergic Blocker, Suppresses Melanin Synthesis by Inhibiting the cAMP/CREB Signaling Pathway in Human Melanocytes and Ex Vivo Human Skin Culture

Catecholamines function via G protein-coupled receptors, triggering an increase in intracellular levels of 3′,5′-cyclic adenosine monophosphate (cAMP) in various cells. Catecholamine biosynthesis and the β-adrenergic receptor exist in melanocytes; thus, catecholamines may play critical roles in skin pigmentation. However, their action and mechanisms mediating melanogenesis in human skin have not yet been investigated. Therefore, we examined the potential anti-melanogenetic effect of carvedilol, a nonselective β-blocker with weak α1-blocking activities. Carvedilol reduced melanin content and cellular tyrosinase activity without compromising cellular viability in normal human melanocytes as well as in mel-Ab immortalized mouse melanocytes. Carvedilol downregulated microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein (TRP)-1, and TRP-2. Carvedilol treatment led to the downregulation of phosphor-cAMP response element-binding protein (CREB). Moreover, the increase in cAMP levels upon treatment with forskolin reversed the anti-melanogenic action of carvedilol. In addition, carvedilol remarkably reduced the melanin index in ultraviolet-irradiated human skin cultures. Taken together, our results indicate that carvedilol effectively suppresses melanogenesis in human melanocytes and ex vivo human skin by inhibiting cAMP/protein kinase A/CREB signaling. The anti-melanogenic effects of carvedilol have potential significance for skin whitening agents.

Vitiligo and anxiety: A systematic review and meta-analysis

BACKGROUND

Vitiligo is an acquired depigmenting skin disease which is often accompanied by mental distress. There are numerous studies dedicated to local and global prevalence of depression in patients with vitiligo but anxiety has not been recognized as a major mental problem within named population. We aimed to evaluate the prevalence of anxiety among patients with vitiligo from different countries and to compare it with patients suffering from eczema, psoriasis, and acne.

METHODS

In November 2019, we conducted a systematic search for observational studies that examined the prevalence of anxiety in vitiligo patients. Fifteen studies comprising 1176 patients with vitiligo were included to our systematic review.

RESULTS

The general prevalence of anxiety among vitiligo patients was equal to 35.8%. Statistically significant difference in anxiety rates was found among female and male patients (47.32% vs 42.4%) (P = 0.03), but the clinical relevance of this issue remains arguable. In addition, the pooled odds ratio among vitiligo and non-vitiligo patients did not indicate a statistical significance among patients coming from different continents.

CONCLUSIONS

The pooled prevalence of anxiety among vitiligo patients worldwide was comparable to other severe skin disorders. This finding accentuates the necessity of anxiety awareness in management of patients with skin diseases.

Premature cell senescence in human skin: Dual face in chronic acquired pigmentary disorders

Although senescence was originally described as an in vitro acquired cellular characteristic, it was recently recognized that senescence is physiologically and pathologically involved in aging and age-related diseases in vivo. The definition of cellular senescence has expanded to include the growth arrest caused by various cellular stresses, including DNA damage, inadequate mitochondria function, activated oncogene or tumor suppressor genes and oxidative stress. While senescence in normal aging involves various tissues over time and contributes to a decline in tissue function even with healthy aging, disease-induced premature senescence may be restricted to one or a few organs triggering a prolonged and more intense rate of accumulation of senescent cells than in normal aging. Organ-specific high senescence rate could lead to chronic diseases, especially in post-mitotic rich tissue. Recently, two opposite acquired pathological conditions related to skin pigmentation were described to be associated with premature senescence: vitiligo and melasma. In both cases, it was demonstrated that pathological dysfunctions are not restricted to melanocytes, the cell type responsible for melanin production and transport to surrounding keratinocytes. Similar to physiological melanogenesis, dermal and epidermal cells contribute directly and indirectly to deregulate skin pigmentation as a result of complex intercellular communication. Thus, despite senescence usually being reported as a uniform phenotype sharing the expression of characteristic markers, skin senescence involving mainly the dermal compartment and its paracrine function could be associated with the disappearance of melanocytes in vitiligo lesions and with the exacerbated activity of melanocytes in the hyperpigmentation spots of melasma. This suggests that the difference may arise in melanocyte intrinsic differences and/or in highly defined microenvironment peculiarities poorly explored at the current state of the art. A similar dualistic phenotype has been attributed to intratumoral stromal cells as cancer-associated fibroblasts presenting a senescent-like phenotype which influence the behavior of neoplastic cells in either a tumor-promoting or tumor-inhibiting manner. Here, we present a framework dissecting senescent-related molecular alterations shared by vitiligo and melasma patients and we also discuss disease-specific differences representing new challenges for treatment.

Plasma & urinary catecholamines & urinary vanillylmandelic acid levels in patients with generalized vitiligo

Background & objectives

Vitiligo is an acquired skin disease characterized by depigmented areas of the skin. Increased release of catecholamines from autonomic nerve endings in microenvironment of melanocytes in affected skin might be involved in the aetiopathogenesis of vitiligo. Levels of catecholamines are considered as being related to onset or worsening of the disease. Therefore, in this study, the role of catecholamines was evaluated in mapping disease stability and outcome of vitiligo patients undergoing melanocyte transfer.

Methods

In this study, circulatory and urinary levels of catecholamine (CA) and vanillylmandelic acid (VMA) were determined in 45 individuals (30 vitiligo patients and 15 healthy controls) using ELISA.

Results

A significant increase for plasma and urinary catecholamines along with VMA was observed as compared to healthy controls. When the pre- and post-intervention levels were analyzed in responders and non-responders, respectively, only dopamine showed significant decline in urine, rest of the molecules in plasma as well as urine showed non-significant decline except VMA which showed insignificant increase.

Interpretation & conclusions

Levels of plasma/urinary epinephrine, and plasma dopamine, could not be established as biomarkers for disease stability or successful outcome of autologous melanocyte transfer in generalized vitiligo patients. However, dopamine (urine) might be of help in determining the stability in patients with generalized vitiligo undergoing melanocyte transfer. Further studies need to be done on a large sample of patients to confirm our findings.

The convergence theory for vitiligo: A reappraisal

Vitiligo is characterized by progressive loss of skin pigmentation. The search for aetiologic factors has led to the biochemical, the neurologic and the autoimmune theory. The convergence theory was then proposed several years ago to incorporate existing theories of vitiligo development into a single overview of vitiligo aetiology. The viewpoint that vitiligo is not caused only by predisposing mutations, or only by melanocytes responding to chemical/radiation exposure, or only by hyperreactive T cells, but rather results from a combination of aetiologic factors that impact melanocyte viability, has certainly stood the test of time. New findings have since informed the description of progressive depigmentation. Understanding the relative importance of such aetiologic factors combined with a careful selection of the most targetable pathways will continue to drive the next phase in vitiligo research: the development of effective therapeutics. In that arena, it is likewise important to acknowledge that pathways affected in some patients may not be altered in others. Taken together, the convergence theory continues to provide a comprehensive viewpoint of vitiligo aetiology. The theory serves to intertwine aetiologic pathways and will help to define pathways amenable to disease intervention in individual patients.

Neural and Endocrinal Pathobiochemistry of Vitiligo: Comparative Study for a Hypothesized Mechanism

The etiology of vitiligo is still unclear. The aim is to investigate a neural and hormonal etio-pathology of vitiligo. Sixty acrofacial vitiligo patients were divided into two subgroups as active vitiligo patients group (AVPs; n = 35) and stable vitiligo patients group (SVP; n = 25). Forty healthy subjects without any systemic or dermatological disease were used as controls. Blood samples were collected, and the samples were used for measurement of free triiodothyronine (fT₃), free thyroxine (fT₄), thyroid-stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), cortisol, estrogen, testosterone, melatonin, and prolactin levels by ELISA, while norepinephrine (NE), epinephrine (Epi), dopamine (DA), homo-vanillic acid (HVA), serotonin, and 5-hydroxyindoleacetic acid (5-HIAA) by high-pressure liquid chromatography. The current results showed a significant increase in plasma levels of Epi, NE, DA, HVA, serotonin, 5-HIAA, melatonin, and in serum level of TSH and prolactin either in SVP or AVP groups than the control group and in AVP than SVP group. The serum levels of fT₃ and fT₄ were significantly decreased either in SVP or AVP groups than the control group. A significant increase in estradiol levels was observed in females within AVP than females in either SVP or control groups. There was a significant increase in serum level of cortisol in AVP than either SVP or control group. There was a significant decrease in serum level of ACTH in either AVP or SVP than control and in AVP than SVP group. In conclusion, there are some neural and endocrine markers that play a pivotal role in pathogenesis and/or consequences of vitiligo. The abnormally disturbed levels of theses markers lead to melanocyte destruction and/or depigmentation.

Focus on Vitiligo: A Generalized Skin Disorder

Vitiligo is an acquired pigmentation disorder due to a disappearance of functioning melanocytes from the epidermis and clinically characterized by achromic patches, often spreading over time. It is still not fully understood how melanocytes disappear in vivo, inducing these peculiar lesions. There are three major hypotheses for the pathogenesis of the disease: the autoimmune hypothesis considers that the disappearance of melanocytes is due to an autoimmune effector mechanism, the neural hypothesis suggests that an accumulation of neurochemical substances is able to damage epidermal melanocytes, and the metabolic hypothesis indicates that an increased sensitivity of melanocytes to oxidative stress is the crucial factor of the disease. Besides these well accepted hypotheses there are also some new interpretations based on a defective adhesion of melanocytic cells, an imbalance in the epidermal production of cytokines and an altered expression of melanocyte receptors. All these theories seem to be based on convincing evidence, indicating that they may contribute in variable proportions to the disease. There is also reasonable evidence at present that vitiligo potentially involves the whole integument, suggesting that it is a generalized skin disorder probably including different cell types during the active phase of the disease. It appears that the different theories may integrate with each other, supporting the concept that in vitiligo there is a final common step, i.e. a loss of pigment in the epidermis as well as different, possibly interacting, pathways leading up to this conclusive result.

Is Lesional Stability in Vitiligo More Important Than Disease Stability for Performing Surgical Interventions? Results from a Multicentric Study

Background:

Ensuring stability of the disease process is essential for undertaking surgical intervention in vitiligo. However, there is no consensus regarding the minimum duration of stability or the relative importance of disease and lesional stability in selecting patients for vitiligo grafting.

Aim:

This multicentric study aims to assess the relative importance of lesional and disease stability on selecting patients for vitiligo grafting.

Materials and Methods:

One hundred seventy patients were recruited into the study and divided into two groups: Group A with lesional stability of >1 year but overall disease stability of only 6-11 months and Group B with overall disease stability of >1 year. Patients underwent either tissue or cellular vitiligo grafting on the selected lesions and the repigmentation achieved was scored from 0 (no repigmentation) to 6 (100% repigmentation). Repigmentation achieved on different sites of the body was compared between the two groups. Adverse effects at both the donor and the recipient sites were also compared.

Results:

Of the 170 patients who were enrolled, 82 patients were placed in Group A and 88 patients in Group B. Average repigmentation achieved (on scale of 0 to 6) was 3.8 and 4.04 in Group A and Group B, respectively. In Group A, ≥90% repigmentation was achieved in 36.6% (30/82) patients, while 37.5% (33/88) achieved similar results in Group B. Additionally, 47.6% (39/82) and 53.4% (47/88) of cases achieved partial repigmentation in Group A and Group B, respectively. Perigraft halo was the commonest adverse effect observed in both groups. Statistical analysis revealed no significant differences between the two groups with respect to the repigmentation achieved or adverse effects observed. Repigmentation achieved was the best on the face and neck area, while acral areas responded the least.

Conclusions:

Lesional stability seems to be as relevant as the overall disease stability in selecting patients for surgical intervention in vitiligo.

Vitiligo--part 1

Vitiligo is a chronic stigmatizing disease, already known for millennia, which mainly affects melanocytes from epidermis basal layer, leading to the development of hypochromic and achromic patches. Its estimated prevalence is 0.5% worldwide. The involvement of genetic factors controlling susceptibility to vitiligo has been studied over the last decades, and results of previous studies present vitiligo as a complex, multifactorial and polygenic disease. In this context, a few genes, including DDR1, XBP1 and NLRP1 have been consistently and functionally associated with the disease. Notwithstanding, environmental factors that precipitate or maintain the disease are yet to be described. The pathogenesis of vitiligo has not been totally clarified until now and many theories have been proposed. Of these, the autoimmune hypothesis is now the most cited and studied among experts. Dysfunction in metabolic pathways, which could lead to production of toxic metabolites causing damage to melanocytes, has also been investigated. Melanocytes adhesion deficit in patients with vitiligo is mainly speculated by the appearance of Köebner phenomenon, recently, new genes and proteins involved in this deficit have been found.

Vitiligo road map

Vitiligo is a depigmenting disorder stemming from melanocyte loss or dysfunction. It has a complex, multifaceted etiology. We constructed a "vitiligo road map," consisting of basic science, clinical, and treatment components, in order to better portray our current understanding of vitiligo pathogenesis and reflect upon novel biomarkers and therapeutic targets for future research. The melanocyte map elaborates on the molecular processes and intracellular signaling pathways initiated by various external autocrine/paracrine factors in representing normal melanocyte homeostatic functions modulating its viability, proliferation, differentiation, dendricity, migration, and melanogenic processes. This vitiligo map identifies known inducers/triggers of vitiligo onset and progression that cultivate a microenvironment for melanocyte disappearance, real or functional. This map describes the molecular mechanisms of currently utilized clinical and experimental treatments of vitiligo that facilitate repigmentation.

Stability in Vitiligo: Is there a Perfect Way to Predict it?

Stability is a hard-to-define concept in the setting of vitiligo, but is nonetheless extremely crucial to the planning of treatment regimens and also in prognosticating for the patient. There are several ways to judge stability in vitiligo, which include clinical features and, recently, many biochemical, cytological and ultrastructural correlates of the same. These recent advances help in not only in prognosticating individual patients but also in elucidating some of the mechanisms for the pathogenesis of vitiligo, including melanocytorrhagy and oxidative damage to melanocytes.

Potential role of neurogenic inflammatory factors in the pathogenesis of vitiligo

BACKGROUND

Vitiligo is a highly complex multifactorial condition of the skin that has an unclear mechanism of pathogenesis.

OBJECTIVE

This review summarizes the role of various neurogenic inflammatory factors significantly upregulated in vitiligo.

METHODS

A literature review was conducted of all pertinent data regarding neuropeptides that are altered in vitiligo and their possible role in the destruction of melanocytes.

RESULTS

The close associations between the skin, immune system, and nervous system, along with specific changes demonstrated in vitiligo patients, support a pathogenic mechanism of vitiligo that involves neuroimmunologic factors, the release of which can be governed by mental stress.

CONCLUSION

Neuropeptides and nerve growth factors are critical regulators of emotional response and may precipitate the onset and development of vitiligo in certain predisposed individuals. More studies are required to investigate whether a direct link exists between genetics, mental stress, and neurogenic factors in vitiligo.

Understanding mechanisms of vitiligo development in Smyth line of chickens by transcriptomic microarray analysis of evolving autoimmune lesions

Background

The Smyth line (SL) of chicken is an excellent avian model for human autoimmune vitiligo. The etiology of vitiligo is complicated and far from clear. In order to better understand critical components leading to vitiligo development, cDNA microarray technology was used to compare gene expression profiles in the target tissue (the growing feather) of SL chickens at different vitiligo (SLV) states.

Results

Compared to the reference sample, which was from Brown line chickens (the parental control), 395, 522, 524 and 526 out of the 44 k genes were differentially expressed (DE) (P ≤ 0.05) in feather samples collected from SL chickens that never developed SLV (NV), from SLV chickens prior to SLV onset (EV), during active loss of pigmentation (AV), and after complete loss of melanocytes (CV). Comparisons of gene expression levels within SL samples (NV, EV, AV and CV) revealed 206 DE genes, which could be categorized into immune system-, melanocyte-, stress-, and apoptosis-related genes based on the biological functions of their corresponding proteins. The autoimmune nature of SLV was supported by predominant presence of immune system related DE genes and their remarkably elevated expression in AV samples compared to NV, EV and/or CV samples. Melanocyte loss was confirmed by decreased expression of genes for melanocyte related proteins in AV and CV samples compared to NV and EV samples. In addition, SLV development was also accompanied by altered expression of genes associated with disturbed redox status and apoptosis. Ingenuity Pathway Analysis of DE genes provided functional interpretations involving but not limited to innate and adaptive immune response, oxidative stress and cell death.

Conclusions

The microarray results provided comprehensive information at the transcriptome level supporting the multifactorial etiology of vitiligo, where together with apparent inflammatory/innate immune activity and oxidative stress, the adaptive immune response plays a predominant role in melanocyte loss.

Potential redox-sensitive Akt activation by dopamine activates Bad and promotes cell death in melanocytes

Dopamine (DA) is a well known oxidative neurotoxin. In addition, Akt has been reported to deliver a survival signal that inhibits apoptosis. However, it has also been reported that chronic Akt activation leads to apoptosis in response to oxidative stress. The objective of the present study was to investigate the possible role of the Akt pathway in vitiligo and its possible relationship with DA-induced cell death using Mel-Ab cells. Cultured Mel-Ab cells were treated with DA with and without N-Acetyl-L-cysteine (NAC), which is known to have antioxidative properties. Cell viability was then assessed by a crystal violet assay and Annexin staining was performed. The changes in the expression of Akt were analyzed by western blot analysis. The cell viability was reduced by approximately 60% in response to treatment with 500 µM DA, and NAC effectively prevented this cytotoxic effect. Likewise, treatment with DA produced numerous Annexin positive cells, while treatment with NAC prevented this apoptotic cell death. Akt was slowly phosphorylated after treatment with DA, while NAC clearly inhibited the DA-induced Akt activation. Western blot analysis also showed that treatment with DA induced the activation of Bad. Finally, LY294002 exerted a protective effect against DA-induced apoptotic cell death. DA may induce redox-sensitive Akt activation and increase the level of Bad, which can promote cell death by heterodimerization with survival proteins. Moreover, NAC effectively protects against DA-induced melanocyte death via inhibition of DA-induced Akt activation.

Erythrocyte malondialdehyde and glutathione levels in vitiligo patients

BACKGROUND

Vitiligo is an acquired and progressive hypomelanotic disease that manifests as circumscribed depigmented patches on the skin. Although the precise mechanism remains to be elucidated, an imbalance of the oxidant/antioxidant system has been proposed as an important etiologic mechanism.

OBJECTIVE

The objective of this study was to evaluate the oxidant/antioxidant status of vitiligo patients at the erythrocyte level.

METHODS

Fifty-three vitiligo patients and 65 phototype-, age-, and sex-matched healthy controls were included in this study. Blood samples were collected from all subjects, and all patients were instructed to answer a questionnaire.

RESULTS

Erythrocyte levels of malondialdehyde (MDA) and glutathione (GSH) were measured. All patients were told to answer a questionnaire regarding their habitual behavior, including frequency of smoking and type of diet. We observed significantly lower levels of GSH in vitiligo patients, but the levels of MDA did not differ between patients and controls. Vitiligo patients who smoked showed significantly lower GSH levels compared to non-smoking patients, but the levels of MDA were unchanged between the 2 groups.

CONCLUSION

From our results, we conclude that reduced erythrocytic or systemic GSH levels constitute a distinctive feature in vitiligo patients regardless of disease activity.

Beta adrenergic receptors in keratinocytes

Beta2 adrenergic receptors were identified in keratinocytes more than 30 years ago, but their function in the epidermis continues to be elucidated. Abnormalities in their expression, signaling pathway, or in the generation of endogenous catecholamine agonists by keratinocytes have been implicated in the pathogenesis of cutaneous diseases such as atopic dermatitis, vitiligo, and psoriasis. New studies also indicate that the beta2AR also modulates keratinocyte migration, and thus can function to regulate wound reepithelialization. This review focuses on the function of these receptors in keratinocytes and their contribution to cutaneous physiology and disease.

The melanocytorrhagic hypothesis of vitiligo tested on pigmented, stressed, reconstructed epidermis

Common generalized vitiligo is an acquired depigmenting disorder characterized by a chronic and progressive loss of melanocytes from the epidermis and hair follicles. We previously proposed a new theory that vitiligo involves the chronic detachment and transepidermal loss of melanocytes caused by autoimmune, neural and impaired redox mechanisms associated with mechanical trauma. In this study, we reconstructed epidermis on dead de-epidermized dermis with normal and/or non-segmental non-lesional vitiligo (NSV) cells and tested catecholamines or sera or hydrogen peroxide. Under unstressed conditions, the number of melanocytes located in the basal layer was significantly lower in reconstructs made with melanocytes from non-lesional NSV skin and normal keratinocytes compared with controls made with autologous normal melanocytes. The number of non-lesional NSV melanocytes was even lower in reconstructs made with keratinocytes from non-lesional NSV skin. Epinephrine and H(2)O(2) could trigger the transepidermal loss of normal and vitiligo melanocytes. Some sera induced melanocyte detachment but without any clear correlation with disease activity in the donors. In conclusion, our results are the first step to obtaining a reproducible melanocytorrhagic model in vitro with some of the stressors investigated. They support the hypothesis that NSV melanocytes have an intrinsic defect, which limits their adhesion in a reconstructed epidermis, with an enhancer effect of the vitiligo keratinocyte milieu.

Oxidation Chemistry of Norepinephrine: Partitioning of the O-Quinone between Competing Cyclization and Chain Breakdown Pathways and Their Roles in Melanin Formation

Aberrant oxidation of norepinephrine (1) via the transient o-quinone has been implicated as a critical pathogenetic mechanism underlying the degeneration of noradrenergic cell bodies in the locus coeruleus in Parkinson's disease, the degeneration of noradrenergic nerve terminals in Alzheimer's disease and following transient cerebral ischemia, and the onset and progression of idiopathic vitiligo. An oxidative pathway of 1 is also believed to account for the slow deposition of neuromelanin in pigmented neurons of the locus coeruleus. Remarkably, after extensive investigations spanning over several decades, there is still a lack of knowledge of the oxidation chemistry of 1 beyond the classic cyclization route leading to aminochrome and lutin intermediates. We report herein that oxidation of 1 in the 50-500 microM concentration range with H2O2-dependent oxidizing agents, such as the Fenton reagent (Fe2+-EDTA/H2O2) and the horseradish peroxidase (HRP)/H2O2 system, leads not only to the known cyclization products, such as noradrenochrome and 5,6-dihydroxyindole (3), but also to a significant proportion of chain breakdown products, including 3,4-dihydroxybenzaldehyde, 3,4-dihydroxybenzoic acid, 3,4-dihydroxymandelic acid, and 3,4-dihydroxyphenylglyoxylic acid, which has never been described among the oxidation products or metabolites of 1. Analysis of the brown melanin-like pigment obtained by oxidation of 1 with HRP/H2O2 gave pyrrole-2,3-dicarboxylic acid and pyrrole-2,3,5-tricarboxylic acid, diagnostic markers of 3-derived units in eumelanins. Comparison with reference pigments prepared by similar oxidation of dopamine and 3 indicated that in the case of 1 oxidative polymerization of indole units through the 2-position contributes only to a minor extent to melanin formation. Overall, the results of this study provide a complete characterization of the oxidative chain fission pathways of 1, highlight 3,4-dihydroxyphenylglyoxylic acid as a novel possible metabolic product of this catecholamine, and yield an insight into norepinephrine-melanin, a putative component of locus coeruleus neuromelanin.

Vitiligo puzzle: the pieces fall in place

Over the years, the role of biochemical, immunological, genetic, and other biological aspects in the pathogenesis of vitiligo has been studied. So far, no convincing model describing the interplay of these contributing factors has been formulated. Based on existing research, we propose that vitiligo has a multi-factorial etiology, characterized by multiple steps, but always involving an increase of external or internal phenol/catechol concentration, serving as a preferred surrogate substrate of tyrosinase, competing with its physiological substrate tyrosine. The conversion of these substrates into reactive quinones is reinforced by a disturbed redox balance (increasing hydrogen peroxide). Such reactive quinones can be covalently bound to the catalytic centre of tyrosinase (haptenation). This could give rise to a new antigen, carried by Langerhans cells to the regional lymph node, stimulating the proliferation of cytotoxic T cells. However, the activation of such cytotoxic cells is only a first step in skin melanocyte killing, which also depends on a shift in the balance between immune defence and tolerance, e.g. resulting from a decrease in properly functioning T-regulatory cells. With this new model, based on a synthesis of several of the existing theories, in mind, the external and internal factors involved in the etiopathogenesis of vitiligo are reviewed, against the background of reported clinical data, experimental studies and existing and potential new therapies. A similar complex mechanism may also lead to some other autoimmune diseases.

Glutathione prevented dopamine-induced apoptosis of melanocytes and its signaling

BACKGROUND

Dopamine (DA), a monoamine neurotransmitter, is a well-known neurotoxin and plays an etiologic role in neurodegenerative disorders such as Parkinson's disease. DA exerts its toxic effect by generation of reactive oxygen species and quinone product. Vitiligo, a depigmentary disorder of the skin and hair characterized by selective destruction of melanocytes, has been reported to show increased levels of DA with onset and progression of the disease.

OBJECTIVE

The aim of this study is to investigate the cytotoxic effect of DA on melanocytes and to search for protective antioxidants against DA-induced toxicity. In addition, molecular mechanism of cell death was also investigated.

METHODS

Cells were treated with DA and cell viabilities were measured by crystal violet staining method. To investigate the cytoprotective activity of various antioxidants, vitamin C, vitamin E, Trolox, quercetin, N-acetylcysteine (NAC) and l-glutathione (GSH) were used. To study cytoprotective effects of NAC and GSH, Mel-Ab cells and cultured normal human melanocytes were pretreated with NAC or GSH, then DA solution was added. DA-induced apoptosis and activation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) were also observed by flow cytometric analysis and Western blotting.

RESULTS

The viability of DA-treated Mel-Ab cells significantly decreased in a dose-dependent manner while keratinocytes were much more resistant to DA-toxicity, which was a consistent finding with the selective melanocyte loss observed in vitiligo. Among various antioxidants used in this study, only thiol-containing antioxidants such as NAC or GSH inhibited both JNK and p38 MAPK activation and apoptosis, indicating the unique protective capacity of thiol compounds. Cultured normal human melanocytes were also susceptible to DA and thiol compounds were very efficiently protective against DA-induced cytotoxicity.

CONCLUSION

DA-induced apoptosis and cytoprotective effect of thiol compounds shown in this study could be a clue to understand pathogenesis of viltigo and provide a new therapeutic strategy.

Dopamine-induced apoptosis in human melanocytes involves generation of reactive oxygen species

BACKGROUND

Previous studies have shown that significant increases in urinary and plasma levels of several monoamines and their metabolites characterize the onset of vitiligo and its progression. Recently, both epidermal keratinocytes and melanocytes were found to have the capacity for the biosynthesis of several catecholamines and serotonin. Some monoamines and their metabolites can induce apoptosis and cytotoxicity in neural cells. However, no previous report has investigated the potential role of these monoamines in inducing apoptosis or cytotoxicity in melanocytes.

OBJECTIVES

To study the effects of dopamine (DA), norepinephrine (NE), epinephrine (EP), and serotonin (5-HT) on melanocyte cytotoxicity and apoptosis.

METHODS

Primary cultures of normal human melanocytes established from the foreskins of normal individuals were treated with different concentrations of DA, NE, EP and 5-HT for 5 and 7 days. Cell viability was measured by the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Melanocyte apoptosis was evaluated by morphological examination and flow cytometric analysis. We also measured the generation of reactive oxygen species (ROS) after DA treatment.

RESULTS

Among the four monoamines used in this study, only DA had an effect, dose-dependently decreasing the melanocyte viability at concentrations ranging from 0.01 to 100 micromol L(-1) (0.1 and 1 micromol L(-1), P < 0.05; 10 micromol L(-1), P < 0.01). In addition, DA-induced melanocyte apoptosis was evidenced by the increased percentage of sub-G1 cells from 7.71 +/- 0.28% (control) to 12.22 +/- 1.05% (0.1 micromol L(-1) DA) (P < 0.005), and treatment with the antioxidant N-acetylcysteine (NAC) reversed this apoptotic effect. DA treatment led to the generation of ROS, which could be prevented by pretreatment with NAC.

CONCLUSIONS

DA can induce melanocyte apoptosis, which might be related to the generation of ROS. This novel effect might play an important role in the development or progression of vitiligo, which is currently viewed as a disease process closely related to melanocyte apoptosis.

Vitiligo patients present lower plasma levels of alpha-melanotropin immunoreactivities

Vitiligo is a depigmenting disorder characterized by the development of white patches with evidence in favour of an autoimmune mechanism. We investigated the role of melanotropins and the plasma levels of alpha-melanotropin and ACTH-like immunoreactivities in 40 vitiligo patients with the aim of detecting a possible influence of neuropeptide regulation of immunity. Twenty-one patients had active and 19 had stable vitiligo disease, 16 persons presented with an additional autoimmune thyroid disease. Median alpha-MSH levels in vitiligo patients were 6.4p mol/l [5.2;11.3] and significantly lower than in control persons with 11.4 pmol/l [8.6;13.4]. Median ACTH levels of the affected patient group were 17 pg/ml [10.5;28] and appeared statistically higher than 12 pg/ml [7;17] measured in the control group. Measured morning cortisol levels in both groups were not significantly different. Reduced cutaneous alpha-MSH immunoreactivities have been related to the development of autoimmune-induced depigmenting disorders. Our data present lower alpha-MSH plasma levels in vitiligo patients which may be associated with the development of vitiligo depigmentation and may indicate a condition of impaired peripheral tolerance in this autoimmune disorder.

New Treatment Modalities for Vitiligo

The development of effective treatment modalities for vitiligo is dependent on an understanding of the events leading to depigmentation. However, the exact pathogenesis of vitiligo is still mostly unknown. Abnormalities in both humoral and cell-mediated immunity have been documented in vitiligo patients and they present a basis for using immunomodulating agents, such as corticosteroids and macrolide immunomodulators, in the treatment of vitiligo. Macrolide immunomodulators, such as tacrolimus and pimecrolimus, which can be used topically, are known as topical immunomodulators (TIMs). TIMs inhibit the action of calcineurin, and consequently inhibit T-cell activation and the production of various cytokines; this is considered the working mechanism of action of TIMs in vitiligo. Several small studies and case reports on the use of TIMs in vitiligo have been published so far. Tacrolimus achieves better results on the face and neck than on other body areas. Particular advantages of TIMs are safety in treating these areas because of lack of skin atrophy and good tolerability. The incidence of application site adverse events in vitiligo seems to be lower than in the treatment of atopic dermatitis. On the face and neck, TIMs may become a useful tool in the treatment of adults and children with vitiligo despite possibly lower efficacy than topical corticosteroids. Further, larger, controlled clinical studies are warranted to determine the definite role of TIMs as monotherapy or in combination with other modalities in the treatment of vitiligo.

Dopamine in the ink defence system of Sepia officinalis: biosynthesis, vesicular compartmentation in mature ink gland cells, nitric oxide (NO)/cGMP-induced depletion and fate in secreted ink

The biosynthesis, localization and fate of catecholamines in the ink gland of the cuttlefish Sepia officinalis were investigated by combined biochemical and immunohistocytochemical methodologies. HPLC analysis of crude ink gland extracts indicated the presence of dopa (2.18+/-0.82 nmol/mg of protein) and DA (dopamine, 0.06+/-0.02 nmol/mg of protein), but no detectable noradrenaline or adrenaline. DA was shown to derive from L-tyrosine, according to experiments performed by incubating intact ink glands with [L-14C]tyrosine. The biosynthetic process involves a tyrosine hydroxylase and a dopa decarboxylase pathway and is independent of tyrosinase. The tyrosine hydroxylase activity was detected under conditions of tyrosinase suppression in the cytosolic fraction, but not in the melanosomal fraction, of ink gland extracts, and the presence of the enzyme was confirmed by Western-blot analysis. Dopa and DA were found to be released from the ink glands by processes controlled through the NMDA-nitric oxide-cGMP (where NMDA stands for N -methyl-D-aspartate) signalling pathway, as apparent from incubation experiments performed with [L-14C]tyrosine in the presence of NMDA, diethylamine NONOate (diethylamine diazeniumdiolate), a nitric oxide donor, 8-bromo-cGMP or a guanylyl cyclase inhibitor. Immunohistochemical results coupled with electron microscopy indicated that DA was concentrated in vesicles specifically localized in the mature melanin-producing cells of the ink gland proximal to the lumen and separated from the melanin-containing melanosomes. NMDA receptor stimulation or exposure to an NO donor caused a marked loss of DA immunoreactivity in mature cells, consistent with a release process. In the lumen of the ink gland, where mature exhausted cells pour their contents, DA immunoreactivity was found to be associated with the melanin granules, due apparently to physical adsorption. Overall, these results point to DA as a marker of cell maturation in Sepia ink gland subject to release by the NO/cGMP signalling pathway, and disclose apparently overlooked DA-melanin interactions in secreted ink of possible relevance to the defence mechanism.

Study on the Antioxidant Status of Vitiligo Patients of Different Age Groups in Baroda

One of the major hypotheses in the pathogenesis of vitiligo is the oxidative stress hypothesis. Pollution plays a major role in the production of free radicals. Gujarat, a highly industrialized state in India has a high prevalence of vitiligo patients. No previous studies were done on the age-dependent antioxidant status of vitiligo patients in Baroda city, Gujarat. Blood samples were collected from vitiligo patients of different age groups (5-15, 16-25, 26-35, 36-45 yr) and from age matched healthy volunteers. Antioxidant enzymes in blood such as catalase, superoxide dismutase, glutathione peroxidase and non-enzymatic antioxidants such as reduced glutathione and plasma vitamin E were estimated. Lipid peroxidation levels in erythrocytes and the reducing equivalent system, i.e. glucose-6-phosphate dehydrogenase were also measured. Significant increase in superoxide dismutase activity and lipid peroxidation levels in erythrocytes was observed in all age groups of vitiligo patients as compared with age-matched healthy controls, wherein an increase of 55% (P < 0.02) was observed in superoxide dismutase activity and lipid peroxidation levels in 36-45 yr age group. Whole blood glutathione levels, erythrocyte glutathione peroxidase and glucose-6-phosphate dehydrogenase activity were decreased significantly, whereas erythrocyte catalase activity and plasma vitamin E levels were not different in vitiligo patients as compared with age-matched healthy controls. No specific age group showed a significant difference. This is the first report on the age-dependent antioxidant status of vitiligo patients in Baroda. The disease affects individuals of any age group as shown in this study and systemic oxidative stress might precipitate the pathogenesis of vitiligo in susceptible patients.

A critical appraisal of vitiligo etiologic theories. Is melanocyte loss a melanocytorrhagy?

Common generalized vitiligo is an acquired depigmenting disorder characterized by a chronic and progressive loss of melanocytes from the epidermis and follicular reservoir. However, the mechanism of melanocyte disappearance has never been clearly understood, and the intervention of cellular and humoral autoimmune phenomena as primary events remains unproven. In this review, is discussed the data supporting the major theories of vitiligo, namely melanocyte destruction (autoimmune, neural and impaired redox status) and melanocyte inhibition or defective adhesion. Based on recent morphologic findings in vivo supporting a chronic detachment and transepidermal loss of melanocytes in common generalized vitiligo, a new theory is suggested proposing melanocytorrhagy as the primary defect underlying melanocyte loss, integrating most of the possible triggering/precipitating/enhancing effects of other known factors.