The response of mammalian epidermal melanocytes in culture to hormones

Intercellular transfer of organelles during body pigmentation

The intercellular transfer of the melanin-producing organelle, called melanosome, from melanocytes to adjacent keratinocytes, is largely responsible for the coat colors and skin pigmentation of amniotes (birds, reptiles, and mammals). Although several hypotheses of melanin-transfer were proposed mainly by in vitro studies and electron microscopies, how the melanosome transfer takes place in the actual skin remained unclear. With advances in technologies of gene manipulations and high-resolution microscopy that allow direct visualization of plasma membrane, we are beginning to understand the amazing behaviors and dynamics of melanocytes. Studies in melanosome transfer further provide a clue to understand a general principle of intercellular organelle transport, including the intercellular translocations of mitochondria.

Gene and protein expression of oestrogen-β and progesterone receptors in facial melasma and adjacent healthy skin in women

OBJECTIVE

Compare gene and protein expression for oestrogen receptor-β (ER-β) and progesterone receptor (PR) in facial melasma and adjacent healthy skin.

METHODS

A cross-sectional study including 42 women with facial melasma, conducted at the Dermatology Service of Botucatu Medical School of São Paulo State University, Brazil. Biopsies of the melasma skin were performed, together with healthy surrounding skin. The gene expression (real-time PCR) of the hormone receptors in the tissue was evaluated. Subsequently, skin fragments were immunostained for nuclear ER-β and PR, evaluated according to their HSCORE (epidermis) and percentage of staining per microscopic field (dermis).

RESULTS

Messenger RNA tissue expression for ER-β and PR showed no difference between melasma-affected skin fragments and the healthy perilesional areas (P > 0.2). Median nuclear epithelial expression for ER-β and PR was higher in lesioned skin (HSCORE 157 and 58) than in the healthy perilesional skin (HSCORE 97 and 19; P < 0.01), with no difference in dermal immunostaining. Nuclear histological expression for ER-β was associated to sun-induced melasma and negative familiar background; PR expression was associated to sun-induced melasma and darker phototypes.

CONCLUSION

No difference was observed in gene expression for oestrogen-β and progesterone receptors in melasma-affected skin compared with adjacent healthy skin. However, the higher protein expression of these receptors in melasma-affected epithelia suggests hormonal participation in the pathogenesis of this disease.

Vitiligo: a review of the published work

Vitiligo is a common depigmenting skin disorder, characterized by acquired, idiopathic, progressive, circumscribed hypomelanosis of the skin and hair, with total absence of melanocytes microscopically. It occurs worldwide, with an incidence rate of between 0.1% and 2%. Vitiligo is an important skin disease having a major impact on the quality of life of the patient suffering from it. The causes of this condition are uncertain but seem to be dependent on the interaction of genetic, immunological and neurological factors. Vitiligo coexists with other autoimmune disorders, Sutton or halo nevus, and malignant melanoma. The substantial disfigurement associated with vitiligo can cause serious emotional stress for the patient, which necessitates treatment. Because its pathogenesis is still not understood, there is a plethora of different treatments. Among them, topical steroids and narrowband ultraviolet B monotherapy were the most common as current treatments for localized and generalized vitiligo, respectively. Cosmetic improvement can be achieved by camouflage products and self-tanning dyes. The course of vitiligo is unpredictable, but often progressive. Spontaneous repigmentation may occur in a few people (10–20%), mainly in children, but this tends to be only partial and on sun-exposed areas. In this article, we review vitiligo as a whole, including epidemiology, pathogenesis and etiology, histopathology, clinical manifestations, classification, clinical variants, diagnosis and differential diagnoses, specific investigation, treatment, prognosis, psychosocial view and its association with other disorders.

[Physiopathology of melasma]

Melasma is a common dermatosis that involves changes in normal skin pigmentation, resulting from the hyperactivity of epidermal melanocytes. The consequent hyperpigmentation is mostly induced by ultraviolet radiation. Clinically, melasma is characterized by light to dark brown macules that usually occur on the face, although they can also affect the cervical and anterior thoracic regions and upper members.Fertile age women and those with intermediate skin phototypes are most likely to develop melasma. Most of its physiopathogenics is not yet fully understood, but there is a relation with genetic and hormonal factors, drugs and cosmetics use, endocrinopathies and sun exposure. The authors discuss the main aspects associated with skin pigmentation and the development of melasma.

Choroidal vitiligo masquerading as large choroidal nevus: a report of four cases

PURPOSE

To describe 4 patients with choroidal vitiligo masquerading as large choroidal nevus.

DESIGN

Retrospective chart review.

PARTICIPANTS

Observational case series of 4 patients.

METHODS

Retrospective chart review.

MAIN OUTCOME MEASURES

Clinical features.

RESULTS

Four patients referred with the diagnosis of large choroidal nevus were found to have unilateral (n = 1) or bilateral (n = 3) extensive patchy choroidal depigmentation classified as choroidal vitiligo. There was no evidence of choroidal nevus, and the pigmented "lesion" proved to be normal choroidal pigment surrounded by a region of pigment absence (vitiligo). There was no evidence of ocular inflammation or related retinal or retinal pigment epithelial changes. The choroidal vitiligo was clinically flat and measured 12 to 24 mm diameter, involving the post-equatorial fundus in all cases. There were no related anterior segment abnormalities. Cutaneous vitiligo was present in all cases. There was no documented progression of the choroidal or cutaneous vitiligo over a maximum 2-year follow-up.

CONCLUSIONS

Choroidal vitiligo is an idiopathic benign process that can involve large segments of the posterior choroid, leaving only patches of residual choroidal pigment, simulating, in reverse, a large choroidal nevus.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Melatonin and the hair follicle

Melatonin, the chief secretory product of the pineal gland, has long been known to modulate hair growth, pigmentation and/or molting in many species, presumably as a key neuroendocrine regulator that couples coat phenotype and function to photoperiod-dependent environmental and reproductive changes. However, the detailed effects and mechanisms of this surprisingly pleiotropic indole on the hair follicle (HF) regarding growth control and pigmentation have not yet been completely understood. While unspecific melatonin binding sites have long been identified (e.g., in goat and mouse HFs), specific melatonin membrane MT2 receptor transcripts and both protein and mRNA expression for a specific nuclear melatonin binding site [retinoid-related orphan receptor alpha (RORalpha)] have only recently been identified in murine HFs. MT1, known to be expressed in human skin cells, is not transcribed in mouse skin. After initial enzymologic data from hamster skin related to potential intracutaneous melatonin synthesis, it has recently been demonstrated that murine and human skin, namely human scalp HFs in anagen, are important sites of extrapineal melatonin synthesis. Moreover, HF melatonin production is enhanced by catecholamines (as it classically occurs in the pineal gland). Melatonin may also functionally play a role in hair-cycle control, as it down-regulates both apoptosis and estrogen receptor-alpha expression, and modulates MT2 and RORalpha expression in murine skin in a hair-cycle-dependent manner. Because of melatonin's additional potency as a free radical scavenger and DNA repair inducer, the metabolically and proliferatively highly active anagen hair bulb may also exploit melatonin synthesis in loco as a self-cytoprotective strategy.

The melanocyte and the epidermal melanin unit: an expanded concept

There are many mechanisms by which melanocytes, keratinocytes, and Langerhans cells interact within the epidermis. Inflammatory mediators affect melanocyte function and melanogenic agents such as alpha-MSH alter the functions of keratinocytes and Langerhans cells. The epidermal melanin unit is better labeled the KLM unit.

Vitiligo

The destruction of melanocytes is the cause of depigmented maculae that clinically represent the disease vitiligo. Although the cause is unknown, various theories such as the autoimmune, autocytotoxic, and neural hypotheses have been proposed. Extensive research has provided numerous answers regarding the pathogenesis, histopathologic evidence, and treatment of vitiligo. This discussion of vitiligo summarizes the varied clinical presentations of the disease, theories attempting to explain the mechanism of melanocyte destruction, histopathologic findings, and different treatment modalities currently available.

Three modes of melanosome transfers in Caucasian facial skin: hypothesis based on an ultrastructural study

The transfer mechanism of melanosome from the melanocyte into the keratinocyte was investigated in mildly photodamaged Caucasian facial skin by electron microscopy. Three ways of transfer are suggested by our observations. The first mechanism probably occurs through the following process: 1) protrusion and insertion of the thick dendrite of the melanocyte into the basal keratinocyte, 2) formation of sac-dendrite complex in the subnuclear region, 3) digestion and segregation of the enclosed dendrite, 4) formation of the cistern in the paranuclear region, and 5) pinching-off of the melanosomes in single or aggregated form from the tip of the cistern. The second mechanism probably takes place through a membrane fusion between the melanocyte and the keratinocyte. Such a membrane fusion possibly forms a passage way for release of the melanosome from the former cell to the latter. The third mechanism is considered to include exocytosis of the single melanosome from the melanocyte followed by the endocytosis through the formation of coated-pit in the keratinocyte.

Increased in vitro expression of beta 2-adrenoceptors in differentiating lesional keratinocytes of vitiligo patients

Keratinocytes were established in serum-free culture medium from lesional and nonlesional skin of a patient with vitiligo (skin type III) and from an age-matched healthy control subject. Both differentiating and undifferentiated cells were examined for the presence of beta 2-adrenoceptors in culture medium containing either low (0.1 x 10(-3) M) or high (1.5 x 10(-3) M) calcium concentrations. Binding experiments were performed with saturating levels of radiolabeled (--)-[3H] CGP 12177, a nonselective beta-adrenergic antagonist. Controls for nonspecific binding were determined by the addition of the beta-adrenergic antagonist, propranolol (5 mumol), before the introduction of (--)-[3H] CGP 12177 to cell cultures. Undifferentiated keratinocytes yielded the highest expression of beta 2-adrenoceptors, whereas differentiating keratinocytes grown in medium with a low calcium concentration (0.1 x 10(-3) M) had a significantly lower expression of receptors with the exception of vitiliginous cells, which retained high densities of receptors, similar to undifferentiated cells. In addition, these vitiliginous keratinocytes showed a defect in 45calcium uptake. In contrast, differentiated keratinocytes from all three cell strains, grown in medium containing a high calcium concentration (1.5 x 10(-3) M) revealed a significantly lower receptor density compared to undifferentiated cells. This finding identified the importance of the extracellular calcium concentration in the expression of beta 2-adrenoceptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidermal changes in active vitiligo

Light and electron-microscopic studies were performed on the vitiligo and adjacent, normal appearing skin from 97 patients with actively spreading vitiligo and 19 patients with stable vitiligo. The vitiliginous skin revealed complete loss of pigment and melanocytes. In addition to degenerative changes in melanocytes, vacuolar changes of basal cells, epidermal infiltration of lymphocytes, dermal infiltration of lymphocytes, and melanophages in the upper dermis were also seen in the normal appearing skin adjacent to vitiliginous skin. These epidermal and dermal changes are more prominent in the skin of actively spreading vitiligo than in stable vitiligo. These findings suggest that the adjacent, normal appearing skin of actively spreading vitiligo shows some characteristic histopathologic findings, especially in the epidermis, indicating that cellular immunity could be involved in the pathogenesis of vitiligo.

An assessment of Langerhans cell quantification in tissue sections

In this paper we look at the regional variation of Langerhans cell (LC) numbers in tissue sections between different sites in the same individual and identical sites in different individuals. We also looked at the reproducibility of identification of LC in tissue sections by their OKT6 reactivity. In this way we could assess the validity of comparative enumeration in random tissue sections. Stepped sections were obtained and stained by the OKT6 method. The slides were projected, the cells counted, and an image analysis system used to measure the length of basement membrane. In this way we could calculate the number of LC per millimeter of basement membrane. Our subjects were six age- and sex-matched volunteers. We found that the number of LC on the trunk was significantly lower than on any of the limbs. However, each individual had significant site variation of LC that was different for each one. This makes direct comparison of individual sections invalid and suggests that the most suitable control, when counting LC in lesional skin, is adjacent normal skin.

A syndrome associating partial albinism and immunodeficiency

Two unrelated patients with partial albinism, frequent pyogenic infections and acute episodes of fever, neutropenia and thrombocytopenia are described. Their pigmentary dilution was characterized by large clumps of pigments in the hair shafts and an accumulation of melanosomes in melanocytes. Melanocytes had few short dendritic expansions, and keratinocytes were hypopigmented. No or few Langerhans' cells were detected in skin by electron microscopy and ATP-ase reactions. This pigmentary dilution, different from all other human albinisms, resembles the unique defect of the mutant dilute (d-d) mouse. Despite the presence of an adequate number of T and B lymphocytes, the patients were hypogammaglobulinemic, deficient in antibody production and incapable of manifesting delayed skin hypersensitivity or of rejecting skin grafts. Their leukocytes did not stimulate normal lymphocytes and could not generate cytotoxic cells during mixed leukocyte reaction. T lymphocytes of one patient were unable to exert a helper effect on the maturation of B lymphocytes into immunoglobulin-containing cells following in vitro stimulation with pokeweed mitogen. This suggests that the humoral deficiency might be secondary to a defect of helper T lymphocytes. Granulocytes did not show any morphologic abnormality, and their bactericidal activity was only moderately reduced. An increased number of polymorphonuclear leukocytes with polar distribution of Concanavaline A (Con A) receptors (capping) was found in one patient and her parents. The family histories suggest that this syndrome is transmitted as an autosomal recessive character.

Effects of 4-tertiary butyl catechol on tissue cultured melanocytes

Depigmenting effects of 4-tertiary butyl catechol (TBC) were investigated using tissue cultured melanocytes of adult guinea pig. Black guinea pig ear epidermis was trypsinized, suspended in BME Eagle media (5 X 10(6) cells) supplemented with 10% calf serum, and seeded in Petri dishes (2 ml/ea). On the 5th day of culture, TBC dissolved in DMSO was added to the media, and the central area of Petri dishes with large numbers of melanocytes (but not keratinocytes) present were examined by light and electron microscopy. After 6 hr of treatment with 1.5 X 10(-3) mg TBC per ml of media, about 15 to 30% of melanocytes detached and about half of the remaining cells showed reversible changes in the cell shapes. An increase of TBC concentration to more than 2 X 10(-3) mg per ml of media resulted in larger numbers of melanocyte deaths. The surviving cells contained numerous, but ultrastructurally unusual premelanosomes and melanosomes. In addition, microfilaments showed a wavy appearance.

Effects of melanocyte stimulating hormone and theophylline on human melanocytes in vitro

The effects of MSH on the human melanocyte in vitro were studied. The addition of MSH up to the concentration of 40 mug/ml into the culture medium did not produce appreciable change on the morphology of the melanocyte. The melanocyte, however, responded to the simultaneous addition of MSH and theophylline with marked increase in the length and complexity of the dendritic process. Melanin synthesis, as indicated by the uptake of tyrosine in the presence of an inhibitor of protein synthesis, was remarkably activated by the simultaneous addition of MSH and theophylline. MSH alone activated the melanin synthesis only slightly, but the increase in the uptake of tyrosine was significant statistically. These results were discussed in terms of the MSH-cyclic AMP cascade in which theophylline worked as an inhibitor of cyclic AMP phosphodiesterase, and increased the intracellular level of cyclic AMP by inhibiting catabolism of cyclic AMP.

Cytochemical identification of ATPase-positive langerhans cells in EDTA-separated sheets of mouse epidermis

Sheets of epidermis for incubation to demonstrate ATPase activity were obtained from specimens of mouse footpad using EDTA as the separation medium. The use of EDTA in place of the NaBr method previously described, resulted in a greatly reduced incubation time, precise localization of reaction product and preservation of ultrastructural detail. A population of closely and regularly spaced ATPase-positive dendritic cells was demonstrated by light microscopy. Electron microscopy demonstrated that, with short incubation times, reaction product was found only in the extracellular space adjacent to dendritic cells, the majority of which possessed the typical ultrastructural features of Langerhans cells.