Melanocortin 1 receptor: what's red got to do with it?

[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.

[Role of genetics in anaesthesia-related variability]

OBJECTIVE

This review discusses variability among patients in anesthesia, due to genetic polymorphisms.

DATA SOURCES

Articles in French and English languages were retrieved from PubMed database. The initial request was "anesth* and (genotyp* or polymorphism* or genetic*)".

STUDY SELECTION

Original articles, general reviews and one case report. Letters were excluded.

DATA EXTRACTION

Rare genetic diseases were excluded from the scope of this review. We stressed on frequent genetic polymorphisms that may have a daily impact in anesthesiology.

DATA SYNTHESIS

Most results were related to pain studies. We selected various examples to describe how genetic polymorphisms impacts the pharmacology of a given drug, and what are the clinical consequences.

CONCLUSION

There is a growing field of pharmacogenetic related evidences in anesthesiology. The results from various animal and human studies underline the genetic origin of variability among individuals. How anaesthesists have to integrate these parameters for their daily practice is still unclear, but pharmacogenetic will obviously be a leading field of anesthesia research in the future.

A review of genetic disorders of hypopigmentation: lessons learned from the biology of melanocytes

Inherited diseases of pigmentation were among the first traits studied in humans because of their easy recognition. The discovery of genes that regulate melanocytic development and function and the identification of disease-causative mutations have greatly improved our understanding of the molecular basis of pigmentary genodermatoses and their underlying pathogenetic mechanisms. Pigmentation mutants can account for hypo-/amelanosis, with or without altered melanocyte number, resulting in different phenotypes, such as Waardenburg syndrome, piebaldism, Hermansky-Pudlak syndrome, Chediak-Higashi syndrome, oculocutaneous albinism and Griscelli syndrome. In this review, we summarize the basic concepts of melanocyte biology and discuss how molecular defects in melanocyte development and function can result in the development of hypopigmentary hereditary skin diseases.

Estudo comparativo morfofuncional de melanócitos em lesões de melasma

FUNDAMENTOS - Melasma é hipermelanose comum caracterizada por máculas acastanhadas em áreas fotoexpostas, cuja fisiopatogenia não é totalmente esclarecida. OBJETIVOS - Caracterizar e comparar morfologica e funcionalmente os melanócitos da epiderme sã com os da pele afetada por melasma. MÉTODOS - Avaliaram-se 12 pacientes portadores de melasma facial, sendo realizadas biópsias da pele lesada e pele sã adjacente. Os cortes foram corados por hematoxilina-eosina, Fontana-Masson, marcados pelo Melan-A e submetidos à microscopia eletrônica. A quantificação epidérmica de melanina e melanócitos foi estimada a partir de análise citomorfométrica digital. RESULTADOS - Todas as pacientes eram mulheres com média de idade 41,3±2,8 anos. Ao Fontana-Masson evidenciou-se importante aumento da melanina epidérmica na pele lesada em relação à pele sã. A marcação pelo Melan-A demonstrou melanócitos maiores com dendritos proeminentes na pele lesada. Observou-se maior densidade de melanina epidérmica na pele lesada, e a análise digital do número de melanócitos da epiderme não demonstrou diferença significativa entre pele lesada e sã. À microscopia eletrônica, observaram-se número aumentado de melanossomas maduros nos ceratinócitos e melanócitos com organelas citoplasmáticas proeminentes na pele lesada. CONCLUSÕES - Melanogênese aumentada na epiderme com melasma em relação à epiderme normal adjacente.

Melanocortin ligands: 30 years of structure-activity relationship (SAR) studies

The challenge of peptide and peptidomimetic research is the development of methods and techniques to improve the biological properties of native peptides and to convert peptide ligands into non-peptide compounds. Improved biological properties of peptides includes enhancement of stability, potency, and receptor selectivity, for both in vivo and in vitro applications. The design of a ligand with specific activity and desired biological properties is a complex task, and, to accomplish this objective, knowledge about putative interactions between a ligand and the corresponding receptor will be valuable. This includes interactions for both the binding and signal transduction processes. Structure-activity relationship (SAR) studies involve systematic modification of a lead peptide and are designed to provide insight into potential interactions involved in the formation of the ligand-receptor complex. It is desirable to have knowledge about both favorable and unfavorable processes that may occur in putative ligand-receptor interactions that result in either receptor stimulation or inhibition. Herein, we discuss various SAR studies that have involved melanocortin peptides over three decades and the information these studies have provided to the melanocortin field.

[Alpha-melanocyte-stimulating hormone. Its current significance for dermatology]

Alpha-melanocyte-stimulating hormone (alpha-MSH) is a tridecapeptide that was originally characterized as a neuropeptide derived from the pituitary gland. alpha-MSH is synthesized from pro-opiomelanocortin (POMC) by the action of specific prohormone convertases which cleave POMC into alpha-MSH, adrenocorticotropin and beta-endorphin. The various effects of alpha-MSH are mediated via melanocortin receptors. The skin as well as the majority of cutaneous cell types express POMC. Proinflammatory stimuli such as ultraviolet (UV) light induce POMC expression and alpha-MSH secretion. Receptors for alpha-MSH are not only expressed by melanocytes, where they mediate melanogenesis and proliferation, but also by virtually every cutaneous cell type. Accordingly, alpha-MSH elicits a plethora of biological actions in these cell types including immunomodulation, protection from oxidative stress and UV-induced apoptosis, modulation of secretory epithelial function and regulation of extracellular matrix composition. These actions may be exploited in future by using super potent and truncated MSH peptides for the treatment of various skin disorders including inflammatory dermatoses.