Expression of endothelin-1, endothelin-3, and endothelin-A and B receptors in the epidermis and upper dermis of the skin with facial melasma, compared to the adjacent healthy skin, in adult women

Abstract

Melasma is an acquired chronic hypermelanosis, characterized by brownish patches in photoexposed areas, especially the face. It mainly affects women at menacme and has an impact on the quality of life and psychological distress. The onset of melasma is related to genetic predisposition in association with individual characteristics and exposure to environmental factors. Chronic exposure to ultraviolet radiation is the most important of the environmental triggering factors. Its pathophysiology has not been completely elucidated, but it involves an increase in local melanin production induced by several melanogenic factors, some of which are already known, such as alpha-MSH, SCF, HGF, KGF, NGF. Other factors have aroused growing interest in the regulation of melasma skin pigmentation, such as endothelin and its receptors. Endothelins are peptides produced by endothelial cells and smooth muscle cells in the walls of blood vessels. They have a powerful effect on vasomotor tone, hormonal production and cell differentiation, assuming a regulatory role in the hydro-pressure balance of the cardiovascular and renal systems. Endothelins are also produced by keratinocytes exposed to ultraviolet B radiation that, in paracrine communication with the melanocytes of the epidermo-melanic units, induce melanogenesis through activation of specific receptors on the surface of the melanocytes, such as the Endothelin 3 Receptor (EDNRB). The increase in vascular elements in the upper dermis of the skin with melasma, accompanied by other RUV-induced inflammatory changes, suggests the association between the increase in endothelin secretion by epidermal keratinocytes and dermal endothelial cells and their melanogenic effect on the overlying epidermis, making up part the complex (and not completely clarified) pathophysiological link between changes in dermal senescence and its effects on the installation, maintenance and relapse of melasma. Although the positive association between endothelin and melanogenesis has already been experimentally established, in addition to high levels of this factor in the epidermis overlying the hypervascularized dermis of benign vascular lesions and in other pigmentary disorders (such as solar lentigo), this relationship has not yet been evaluated in a way systematically in the skin affected by melasma. The present study aims to evaluate the tissue expression of Endothelin-1, Endothelin-3, and of Endothelin-A and -B receptors in the skin with facial melasma compared to the adjacent healthy skin. This project is a cross-sectional study involving skin fragments (punch biopsy 3 mm from the melasma and adjacent healthy skin) of 20 adult women (e 18 years old) with facial melasma. The research participants were women with facial melasma who had been untreated for at least 30 days prior to biopsies, except for the use of sunscreen. A reanalysis of the skin fragments obtained and studied in a previous project will be carried out: "Assessment of autophagy and senescence in the epidermis and upper dermis of the skin with melasma compared to the adjacent healthy skin", which was submitted to the FMB ethics and research committee - UNESP and approved. The fragments, from both topographies, after dewaxing, will be subjected to triple-labeled immunofluorescence: (a) anti-Endothelin-1, anti-vimentin, DAPI; (b) anti-Endothelin-3, vimentin, DAPI; (c) anti-Endothelin-A Receptor, anti-vimentin, DAPI; (d) Endothelin-B Receptor, vimentin, DAPI. The resulting slides will be photographed under a fluorescence microscope. The intensity of the markings will be assessed quantitatively using the ImageJ software and the markings will be compared between the skin with melasma and the adjacent healthy skin, in the following cells of interest: keratinocytes, melanocytes of the basal layer, pendulum melanocytes and fibroblasts of the upper dermis. (AU)